probably 461's, or 292's.
http://www.customclassictrucks.com/techarticles/0405cct_vortec_cylinder_heads_small_block_chevy/index.html This will answer all your questions. Yes it can be done. There's a bit more to it than just torquing on a new set of heads, but if you can replace heads, you can more than handle the rest of it. Should flow much better than the stock TBI heads. Vortec heads flow far better!
If you're wanting very streetable power then you need to take a look at AFR (air flow research) heads. They took a stock 302 ford, did nothing but change the heads and it gained almost 100hp. Howerver for big block applications I would look into the Brodix line.
5.3 cylinder heads bone stock with180,000 miles flowed maximum of 288 cfm at .700
Yes, but running a 350 cam with 305 heads is not effective,you need to run 350 heads as well. In order to benefit from a 350 cam you need something to flow that extra fuel and air, so using 350 heads along side of the 350 cam will be the cheapest and best choice. HAVE FUN!! A 350 head can physically bolt onto a 305 block. However, 350 heads can have the valves extend into the cylinder and contact the cylinder wall (even with the smaller 305 cam). The 350 cam in the 305 with stock heads will work. You wont want to use 350 heads you will lose compression due to the largers combustion chambers.
the oil drain holes in the heads may be stopped up
No, those are low compression heads 8:1 I believe and they won't flow any better.
In a 1996 350 LT1 Chevy model, the water pump pumps water into the heads directly through?æa hose. The water does not flow through the?æinternal water jacket.
You would also have to change the intake manifold, with the heads. I feel compelled to advise you, you are going backwards in technology, thus less performance, and mileage. The newer heads flow better. However, I understand the need to get on the road cheaply, so if you use the older intake, yeah, you could do it.
flow
It is a flow.
Flow
yes, production is a stock concept and income is a flow concept.