Greg, The vortec heads are for the 350 engine with combustion chamber size to match. The 350 has a 4 inch bore and the 305 has a 3 3/4 inch bore. You will lose compression ratio big time. The valve stem seal replacement job is not a really difficult job and if you are good with tools you could do it yourself with the proper tools, if not talk to your local machine shop operator. That of course will mean disassembly, much more of a job than valve stem seals.