No. The 350 has bigger valves. While you CAN put the 305 heads on the 350, (I can't imagine why you would actually want to) you can NOT put the 350 heads on the 305. Because of the 305's small bore, the valves on the 350 heads will hit the cylinder block.
No it Has a different bolt pattern because of the engine size
No 305 heads bolt up different then 350 heads If they are 305 vortec they will bolt up. However they do not have the same flow. The 305 vortec head has smaller runners, smaller valves and does not have the same heart shape combustion chamber. Now if you meant the older 305 heads onto a 350 vortce then no they will not. The vortec uses raised runners and the ports will not match. On top of it all the 5.7 vortec has more flow then any other production head. Placing a 305 head in its place would be going backwards.
Yes, but I don't know why you would want to use them on a 350. 305's are limited as far as valve size is concerned because their small bore causes clearance problems with the large valve heads... Larger valves will actually hit the block on a 305. Just about ANY 350 head is better than ANY 305 heads.
Yes you can. There are a few sensors that are different but after swapping them over it will run. The mounts and bolt pattern are the same. You will certainly be stepping back as far as performance and power goes. Not only does it obviously have fewer cubic inches but the heads lack the flow that the 350 vortec heads have, The 305 Vortec heads also do not have the famous Vortec heart shaped combustion chamber as the 350 heads. The 305 head also has smaller valves and smaller runners. You can also swap the other way and place a 350 vortec in where a 305 was. I have personally done these swaps with no troubles at all.
Yes they will with no problems. They are basicly the same heads, Just different CCs.
Yes, they will work. but you wont gain power because the little 305 isn't putting out enough flow to keep up with the heads
== ==
no they will not
no
Yes their the same block....
Yes they will fit right on there with no machine work are problems.