(Newbe) 273 to a 340 and tremec 5speed swap.

For a "Newbie" you seem insistent on biting off more than you can chew, coming up with elaborate swap ideas for the most work and fab imaginable in your efforts to do a cheap flip. Just get a 318, a crank flange bushing for your pre-'68 transmission, bolt it in and sell it. Other than the flange bushing, it's a straight-up "unbolt the old and bolt in the new" swap; no parts chasing, fab or custom work. Done.
i understand completely were your coming from. but i have a problem with going a little crazy on all of my projects! you sound just like my dad witch completely proves him right lol. i just think haveing a 340 360 or bigblock with (especially) a stick shift would be so much fun and such a cool talking point. if i can build my dream cuda and still make money on it then thats a hard thing to tern down. i appreciate your comment, being completely grounded in reality is very helpful for me. stay safe,
George.