> where you would recommend getting models from for 3d printing
Have you checked the Armory right here on the 405th site? There's also thingiverse, believe it or not. One of the most prolific modelers ("MoeSizzlac") is continually putting up models there for free. And then Etsy has a number of modelers selling their files there.
The best advice I can give is to look closely at the files you get and compare them to your own build. Most people model for their own use and body type because its just natural and easiest to print and test fit before putting them on the market. So the slender person makes models for a slender build and might bulk-up the files to make them look muscley. That doesn't work well for the guy that's already a stocky build. I've been bit by that case along with a couple others I've seen. Then again, the guy that makes files for the muscular fella doesn't help you if you are of a petite build.
There's probably a dozen build thread here for people that already did the Mark V armor. At least a dozen. Take a couple hours and read through them. What files did they use... what were they complaining about in their build thread... what did they like... There's hundreds of man-years of experience already documented in detail, history, description, photos and so on here. It would be a shame to take advantage of it.