This. I wouldn't spend any money to build a 305. If I had one in good condition that was ready to drop in, and I had a disposable POS commuter truck, then I'd drop it in and immediately put a "for sale" sign on it. Otherwise I'd strip all the 350 compatible parts off it and run it to the scrap yard for some short iron dollars. A 305 is more valuable as scrap than it is in rebuildable condition.305’s have small bore and tiny combustion chamber cylinder heads that limit a good return on investment in camshafts. They are completely unremarkable in almost every aspect. Low torque and horsepower but not way better fuel mileage as you would expect.
The 350 TBI block is your best bet with the one piece rear main seal, and it likely has roller cam provisions. It's exactly what your truck came with in the first place. Get the factory roller bits from Pull-A-Part - roller lifters, dogbones, spider, pushrods, and cam retainer. If you don't have roller provisions, drill and tap the mounts yourself.
I put Vortec heads on the 350 in Way Cool Jr. If you can find them cheap, they're worth it, but be sure and have them magnafluxed! About half of the junkyard Vortecs have cracks.
If you're spending good money on heads, you're not going to beat the AFR Enforcers for the price.
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