I came in a little late but check out the G838.org site. It is M151 only. A lot of good info on there. Check the underneath very well. They rust out badly under there and they are unibody so no frame. If it is rotted on the rear crossmember then walk away.
To the original poster...spend all your time looking at the body. Get dirty...crawl underneath...dont be afraid to tap and poke and look with some REALLY good light. Be ultra suspicious of any new undercoating because it usually masks stuff the vendor doesn't want you to see. Pay attention to rust, rust, rust, rust...even if you do nothing else...and spend a *lot* of time underneath...95% of your appraisal of the vehicle. Consider working brakes and drivetrain to be a bonus.
Rear crossmember (the one just behind the seats underneath) is a bitch, as it doesn't come with the famed 'Large Rustout Kit' which you'll hear lots of people talk about. In fact, in the instructions that come with the Rust Out Kit made by AMG - they tell you to condem the whole body if that crossmember is rotted out.
But...if you have a lot of patience, skills and equipment (or a friend with same) you could fabricate all of that again if the rest of the vehicle body is sound. Generally - if that frame member is toast...it won't be the only one. One of mine was taken off the road because of rot there, and when I checked it out a bit further - there was a ton of rot in the rear as well. Thankfully the longitudinals are still good.
Pay close attention underneath where the longitudinals would've been cut and rewelded as that's a major structural deal. There are lots and lots of really bad weld jobs, checker plate jobs and even worse out there. One guy put wood in the frame channels and just ran bolts through both halves and put it back together that way with some sheet metal work upstairs!
$2500...hard to go wrong...even if the weld job isn't up to scratch there's nothing stopping you from recutting it and rewelding properly if the rest of the body is in decent shape -- especially if you get a title with it.
A2 was less tippy than the plain model and A1 model because they went from 'swing arm' VW type suspension to 'trailing arm' type with the A2s. The Army tried several mods on the plain model and A1 model vehicles to restrict suspension travel including welding on a length of chain each side. I've driven both models extensively (and an A2 for a daily driver for nearly 10 years) and only had a soiled shorts moment twice - both times with the straight M151 with the early suspension.
They're phenomenal vehicles - still my favourite 1/4 ton out of all of them...even foreign speedier things like the German and Canadian 'Iltis'. They ride beautifully - have a great turning circle - handle bumps and logging roads and worse without making you swallow your back teeth as with a solid axle vehicle -- and as long as you drive sanely and keep an eye on your rear suspension bushings...life is good.