I'm Cummins swapping a '74 Duster, thought I'd share the progress.

in addition to all the aforementioned issues: weight, heat, cooling system, fuel, which you know going in are issues, i hope that your fabrication/chassis building skills are en pointe.

sectioning the firewall and moving/modifying the crossmember and floor means that you're compromising critical structural components of the car. this is well beyond the purview of "connecting the front and rear subframes". you should be thinking cage plus reinforcements in select areas.

handling wise, you'll never meet a corner you like.

i applaud the idea, but if i were hankerin' for the coal my choice would be a 4BT