I think if you get the mounts from a 69 to 70 and maybe 71-2 big merc and LTD with a 429 a 429/460 could be bolted in. The frames look identical with the exeptions of where the bumpers bolt on to the frames back to 65,I am thinking about doing the same to my 65 country squire when the 390 gets tired. 73-78 big car mounts might work too.