390 vs 408

if budget is concern...

the 360/408 had more pistons to choose from...rings are cheaper since they are based off a 4.00 bore..shares chevy and ford engines...

the 318/390 ...either diamonds pistons or KB pistons ...rings are more expensive..smaller bore ..less cubic inches...

you should write out on paper and compare prices between the two...and see which engine is in the best shape and it could save you money in machine work...