engine rebuild

is your car a numbers matching car?? cause I wouldn't bother with rebuilding it unless it is, other wise you have a ton of options as far as 318,340, 360 etc. I rebuilt the top end of my 318 I used to have in my duster and that resulted in blowing out the bottom end sealing the top put more stress on the bottom so after a short time the rings were bad and it was using a lot of oil. IMO you shouldn't do just the top cause the bottom wears out same as the top unless you know for sure your bottom end is in good shape ie; you've had it rebuilt etc..