FordMan, thanks. I will inspect those areas. I'm a little fuzzy on the location of the transmission mounts and lower(?) engine mounts, do you know of any resources or videos for replacing those? My lower control arms are worn, they've been crowbar-ed out of the way a lot for other repairs, perhaps their time has come.
QUICKSILVER, I do remember reading that some clunks can be related to the steering system. I'll try to inspect the rack and pinion mount bolts. Again, I'll have to find them first :3
Here is a quick video of shifting the car into reverse. The first noise when I shift is obviously the doors locking, but listed for the rumbly sound and the loud clunk.
https://youtu.be/szKdJy7rj2k
