when putting a 6bt into a 69 gmc truck you only need to have the provision for an orifice tube to mate the new cummins stuff to the old truck stuff---i would talk to one of the AC guys at tubes and hoses---i had such a project going and was about to get the hoses mated together when i got mowed down by a crazy driver----on the hole in the firewall for the plenum they are different and will take some work....