Any thoughts on the aftermarket voltage regulator? Where to put it ? The trash? There's no a lot of room in the headlight after the wires and globe go in

Don't ask me how I did that getting the text jumbled around

Yep i jumble text too. It's something to do with when or how you add pics--before--during--or after--i dunno. I go back later to try & close it up if its too bad & spread around. All readable though, just gotta look for it.

I am pretty sure your air box is the same as a 1976 DT250 or DT400, the 1976 DT250 and DT400 came factory with a voltage regulator and has a provision on the air box to mount the factory voltage regulator, you would have to run some wires to wherever you plan on splicing in your voltage regulator to your 1974 harness.

Thanks for your responses . I'll check out the airbox there is a place on the left side of the air box that I've been wondering about

The PO of my 250 zip tied it to the upper left side of the frame as seen in this photo. Not saying I recommend that method, but that's how it remains today. 
 

Thanks Schu, I did reference the service bulliten in the tech library, I like the idea of mounting it to the outside of the headlight shell , and I recall reading somewhere here on the forum that a person made a pigtail and attaches it to the blue wire from the tach and simply plugged into it instead of a splice , I was hoping someone could help me find that write up.
Thanks again.
John

I believe member DEET makes a pigtail for plugging in a regulator so you don't need to splice wires. 

Thank you MarkT for that info on the pigtail.
I also want to say thank you for your reply in another post  Wiring Help, Advice, Wisdom Needed ... DT250A.you have given me a better understanding of the electrical system and how simple this is.  I think you also posted somewhere else regarding working one thing at a time . I have to remember to look at the color of the wires carefully as the colors are not perfectly identical from different components to the enduro doctor harness such as my aftermarket handlebar controls but they are close . I spent more time today getting the clutch & throttle cables installed and the oil pump and hoses and fine tuning the harness layout. I getting close, i made a list of a dozen things that still need to be done . My original exhaust needs cleaning inside the tail pipe looks plugged , a small chunk of metal fell out of the big pipe , maybe part of the baffle? Any tips on cleaning out the exhaust is greatly appreciated. 
thanks again 
john 
 

As simple as it seems while I'm sitting in my recliner , I'm sure I'll have more questions when I get back out in the garage