As others have said, it would be one heck of a lotta work. Nothing's impossible....some things just take more time, money and effort...not to mention ingenuity.
However, if it was me, I'd stay with the Bowties. A .030 over 400 smallblock gives you 406 CID (.040 over...the safe maximum for a 400) is roughly 409. It'd be kool to say that you have a 409-powered truck. I may do this when I rebuild the 400 in my El Camino.
Then there's the big blocks. 396, 454...a little boring and 468 or 472...A lotta latitude that way. If you wanted to go nuts, you could get a 502 CID crate motor from GM. I know a guy who runs one in a 41 (or so)
Diamond T. It's a very kool truck.
I've considered putting a 392 or 426 Hemi into my 63 Nova, (it has a 355 and 4-speed at the moment) just to be different...but I don't think it'll ever get past the "thinkin about it" stage.
Good luck with it,
