I'd just bolt the new one on rather than go changing coils. Hope the old flywheel fits over & works but you'll soon know. If it were me going for the easy way out i'd just bolt it on with screw where you can see they've been on the new one, then check the points gap by eye & 15 thou is pretty easy to judge--when doing it for 60 years plus lol-- & timing should be close. But could check with something down the plug hole & mark 3.2mm before tdc as best you can for points cracking 'just'. Lighting wires your yellow will be highest output but hope you have a regulator or bulbs will be shot unless a good battery is in the circuit. If no battery fitted then & regulator will save them. Or if ya running a simple lighting system with no battery or regulator just pick one of the other lower output wires from the lighting coil. Trial & error but be careful revving it with the yellow high output. Or ignore me--i'm woffling now i read it lol.

I would not use that stator unless you have the matching flywheel which it sounds like you do.  You should be able to see where the 77 stator was set in the slots by the marks from the screws... should be near center of slots.  Bolt it there and then I'd set the timing correctly.

If you decide to use the 77, you absolutely must use a voltage regulator in the headlight circuit.

You'd connect the single green out of 77 stator to both greens on 75 bike.  Black/white is the points wire, same as your black now. Yellow to yellow.   Sky blue obviously isn't needed.

 

Thanks much, RT325 and MarkT.  Sorry for the slow response, but storms had my power knocked out here for the past 5 hours.  Well, I plan on making a trip back to the salvage yard just to check the other Yamaha DT engines he has for a possible "exact match" to what I have now, but if there's nothing there that is better than this '77, I will put that entire stator (along with its flywheel) into my bike and then set the timing according to specs.  Just so we're clear, MarkT...there shouldn't be any problem connecting the single green out of the '77 stator to BOTH greens on my '75 harness?  I'm not 100% sure why the '75 has the two greens, but is it perhaps for the "lights on" / "lights off" switch that I repaired the other day?  And yes...I did already wire a brand new regulator into the headlight per the Yamaha service advisory.  I'll keep you posted as to the results once I get this done.  Might not be tomorrow, as there are a lot of trees down that will need to be cut up in the morning.

You could also do a VAPE 12v conversion.
Then you have new flywheel, complete new electronic ignition, flasher rely, regulator, ignition coil, plus proper 150 Watt charging including better headlicht.
Price is about 300 USD and you can sell your old stuff...
I did hunting on an used fitting stator and coils on Fleabay for month. The one i bought was poor, also. But knowing what i know now, i´d better converted directly to VAPE.
Regards Guido

No panic to get back. I've got trees to do over at my neighbors place too as it happens. The "77 stator you have will be good with the 77 flywheel as Mark pointed out, but i wasn't sure. Also important to hold the flywheel solidly while tightening. Ok i probably overdo the tightening but never slip. Here's a pic of a similar tool to the one i use. I hold it solidly on the footrest in this case. Pics coming. Sounds like you have a proper flywheel puller, the 27x1 LH thread puller so that's good.No panic to get back. I've got trees to do over at my neighbors place too as it happens. The "77 stator you have will be good with the 77 flywheel as Mark pointed out, but i wasn't sure. Also important to hold the flywheel solidly while tightening. Ok i probably overdo the tightening but never slip. Here's a pic of a similar tool to the one i use. I hold it solidly on the footrest in this case. Pics coming. Sounds like you have a proper flywheel puller, the 27x1 LH thread puller so that's good.

Thanks RT325. I'm more than a little hesitant to use that type of tool to hold the flywheel though, as if I had to guess....I'd say that's how the previous owner scraped across that lighting coil.  While I do have that type of tool, a mechanic buddy of mine has a strap holder that goes around the outside of the flywheel so I'll probably use that just to be safe.  I know the tool you mention has great holding power against something solid like the footpeg, but my luck would be to have it slip and I'd be back to square one...LOL.  Any idea what the tightening torque is on the flywheel nut (assuming Yamaha listed one)? Thanks!

Yes fair enough. Mine has short pins but still gotta be careful. Personally i just think a strap is too forgiving but that's me lol.

I think the reason fpr your damaged coil is this tool, sombody used, not the one, RT325 has.
 

Well...I'm making progress.  I got the timing set and the bike runs great!  Thank you all for your help.  I was actually unable to use the dial indicator that I just bought because one of its rods was too short and one was too long...so I just marked TDC and 3.2mm BTDC on a small skinny screwdriver and used it as my "measuring device."  Apparently I must have been either spot on or close enough because as I said, the bike runs great.  Sadly, as has been the case with this bike since I got it 2 weeks ago, as soon as I fix one issue, another one pops up.  As I returned from the test ride today after setting the timing, my buddy noticed that my tail light would "flash" along with the turn signal when I would activate either the left or right turn signal switch.  I honestly thought I had all the wiring sorted out, as this never occurred when I tested the turn signals with the bike not running.  Then, after I turned the bike off and tried the signals again (just running them from the battery), all lights were dead and I saw that I had blown the main fuse off the battery.  The wiring from the rear turn signals and to the tail/brake light is all going to be redone tomorrow and I'll look for good clean grounds on all of it.  Also, I just replaced the flasher relay with the one sold on eBay by "pobit", as it was supposed to be much better than the OEM relay.  Anyone here have experience with the relays he sells?  I'm hoping to sort out this issue tomorrow so I can move on to the next issue....the non-functioning tachometer!

Sounds like all my bikes--just work in progress. Hope you find the short circuit. I guess blinkers & tail were running off the magneto when they were all pulsing--flashing. Just a wild guess but wonder if there's a short in the brake light side of things which blew the fuse when brakes applied. Don't read too much into that & just a random thought.