Aware of the small block to big block trans differences, thanks though. As the post I started this with states, the 426 has a proper trans included. My thoughts are that I can use my current trans with a 340/360 I might get instead to avoid the large block install hassles.
Don't underestimate your crusty 273. You may already have a forged crank in there and a wonderful mechanical lifter set. If you put a good cam and piston set in there and the right 4 Barrel you would be down town Julie Brown. LOL