Oddly enough there was a series of articles in a contemporary car crafting magazine during the last six months or so that featured a Blue Oval 302 vs a GM 305 and which discussed the various options open to the two engines. The biggest problem with the 305 is its bore. Being under 4", there is little available by way of performance upgrades. You can swap cams and associated valve train components but the heads themselves are the limiting factor and there is apparently only one manufacturer that evens offers a performance head. The reason for this lack is, as I mentioned a sentence or two earlier, the small bore. Being under 4", you can't use most of anybody's heads because the valves will crash against the cylinder walls. Overbore to 4" is a wasted exercise; simpler to scare up a 350 block and start with that 4" bore. The same restrictions go for pistons and rods and cranks. As someone else mentioned, 334 cid is the biggest you can take a 305 out to. At that point you pretty much have an old school 327 that has been bored around .010" and the 327 is a better motor to start with. If the numbers matching aspect is as much of a concern as you say, then you might give some thought to finding a year correct 350. Your 305 motor is likely to be a Vortec piece anyway; I have one from my Monte that was plugged in by a prior owner and nothing from it is correct for my build. What you would be seeking is a Vortec 350 from any 87 Chev/GM that came with one from the factory. For what I am doing, my mill came from an 85 Chev truck, year correct. That is as correct as I need it to be because this build is not a 100 point special by any means. So maybe a couple of Saturday strolls through your local pick-a-part and see what turns up. Just a thought