If it's a 427 replica, then an FE all the way...with single 4, dual 4 or Webers?
Next, the transmission...traditional 4 speed Toploader? Tremec? 5 speed? 6?
Rear end...what ratio? (first decide on transmission above)
Then the sidepipes...chrome? ceramic coated? stainless? What size?
See, this is a sickness shared by most on this site and we have all been through it. You will twist and turn, make mistakes along the way and tear things out and throw them in you "mistake pile" until one day you say "OK, now that's what I was talking about!"