74 d200 Question
I've got a 77 1/2 ton factory 440. Mine will sputter on hard acceleration. I believe from a weak accelerator pump. It should have a thermoquad on it.
My truck will clunk when going into reverse, thought it's a full time 4X4. I believe the clunking is a combination of loose chain in the T/case, along with the normal gear backlash of the differential and axle shaft spline play.
As mentioned though, it's easy enough to climb under the truck after "blocking the wheels" put it in neutral and then checking all the u-joints for wear.