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: