Appreciate you may just “want it done” but is there something specific you’re struggling with ? I ask as you say to just finish it off ? Whilst I’m no expert I have put a few together over the years for myself and a few friends it may just be a case of some simple guidance to help you get to the end .
I’ve had no problems running standard TM pistols on Green gas in nearly 20yrs , in the height of summer you might want to drop down a bit . All my converted TM pistols run happily on propane .
YMMV .
in my experience if you want functional , the least amount of fuss and most amount of upgrade parts I’d stick with TM or at least TM based & compatible .
however , that is just my experience 👍🏼