Hello!
Sorry to post so late - I found your thread just now.
Let me post a link to my quad 50 build - maybe it could help you some:
www.vietnam.net.pl/M55en.htm
As fot your build I like it very much. You already packed a lot of great details in your build. Things to watch on the quad would be:
- the trailer tow bar - would most likely not be present on a setup like this - especially if the wheels are gone, too. There are two pins to disconnect it and then just a length of tube stays with the gun base. The dragon kit even has a detail that hints at those pins.
-the sight - while handy for shooting fast moving flying targets, it breaks easily and wasnt used for shooting at ground targets. Tracers were apparently enough to aim the quad adequately.
-the power loader - the little engine that loaded the battery constantly should be of newer design (sixties). The older power loader, like shown here: www.vietnam.net.pl/M45quad.pdf was no longer used in Vietnam.
As for the truck - from what I heard, the M35 trucks (deuce and half = 2,5 tons) were considered too light for the job. A 5 tonner - M54 would be a better match. But of course there were some M35s used, too.
Hope I could help you with the above - good luck with your build and I hope my gun truck will turn at least as good as yours when I finally get to build one... Thanks for sharing and have a nice day
Paweł