1998 Ford E450 Super Duty Triton V10- opinions?!

Lots of things can cause clunks. Suspension bushings or other similar items are a definite possibility, and repair cost would be rather variable depending on what it is that needs replacement or adjustment. It could also be something sticking from non-use and work itself free with a bit of driving.

Frequently when I get clunks, it's because I failed to close a door or drawer or left something unsecured in a cabinet or such like.