70-71 Duster??

If the 8 3/4" Is posi or non posi, Could be big $$$ factor.
Also what gearing and bolt Pattern in rear gears n axles are $$$ too

The 318 can make some decent HP with a rebuild.

The 904 can take all the HP the 318 can dish out (with stock rebuild + imo a converter)

Look for the typical Rust areas... Decide what that will cost to fix.

Interior condition... Whats reuseable whats not...

Allways a hard decision on what to offer.. Take paper n pen maybe write down plus n minuses maybe?

Just my .02 Hope it will save ya $ :salute: