I realized when I picked up this old Frankenbike DT2 that it was a mix of parts but now that I got the engine back together and fired up once, after 100 kicks, that the head is different or what appears to be a MX head. Is there a difference in compression?

Yes, the MX head has higher compression.  The specs are (I think) in the tech library.

Just a heads up on the hard start.  I thought I knew a lot about bikes but I tried to start my DT175E in the freezing cold and kicked it over too many times with no firing.  Got it going at last and once it fired it would start first kick every time after that.  I was disappointed that it was so hard to start but was reminded by friends how cold it was.  Then I read somewhere that choke on and no throttle for cold starts. Tried again the next day, equally as cold and it started 2nd kick.  Subsequent tries on different cold days and starts like a champ on first or second kick.

Moral of the story.... even when I thought I knew it all, I should have read the manual. 

I gave up on kicking this am and decided to replace the condensor as the spark is pretty weak. Now its just every now and then

Problem solved. Coil to frame wasnt grounded well or adj point gap to .014. Either way bump started it. This was the first ride thru the gears with fresh bore and bike sat for prolly 15yrs outside in Central Tx. The bottom end has never been opened. All i did was change fluids, ign condensor, cleaned/gapped points, cleaned out the carb and installed a ebay pipe which is prolly crudded up. Just gotta bleed the oil pump and get r on the road!

Just to be clear on the DT2, the choke lever up is off correct? I hope that's right, as that's the only way it will run.

Yes lever up is off but should still run with it on--lever down except if its doing its job of enrichening then need a bit of throttle to stop it drowning out on a closed throttle. But--if the choke fixed jet in the bowl cavity is blocked then opening the choke only opens the airway & would make cold starting likely impossible or when it starts it would rev quite high due to the extra air & no more fuel. Anyway--lever 'up' for normal running.