Can you put 350 TBI heads on a 305?

Yes, all 305-327-350 small-block Chevys share the same bore, except the sb 400. Make sure you check (2) things - 1 - The piston-valve clearence - especially if you're using high-compression pistons, a high-lift cam, 2.02" valves, or a very small small head chamber size. 2 - Note that you may increase the compression ration to a value that requires you to run high-octane gas or retard the timing to a point that defeats the purpose of the upgrade.