The headers for a 350 and 305 are the same.
Your question is a little vague, so im assuming you're asking which is better between 350 and 305 heads. Many people will tell you it doesnt matter. I think if you have a 350 engine then you should use 350 heads. the 305 heads will have higher compression, which will make the car louder, and somewhat faster, however, if you use 305 heads on a 350 engine then you should use a high octane fuel, so it will be better on your engine. Only use 305 heads if you know what your doing. if not you should probably stick with 350 heads. i hope that answered your question.
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.
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.
No. 305's have small valves due to the 305's small bore. Large valve heads can't be used on the 305 because the valves will hit the cylinder block. 350 heads breathe MUCH better than 305 heads. Stick with the 350 heads.
If both engines have a carburetor on them, THEN NO. They will interchange.
Yes
no
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.
You will need to have the heads for the 305 bored out to the same size as the 350. I disagree: you can use the 305 heads on the 350 block but you will increase compression as the 305 heads have a smaller combustion chamber. The critical dimension is valve clearance. If compression ratio is a critical consideration, different pistons may be available which will bring the combustion chamber back to size. the 305 is from the 3.671 inch bore family. The 350 is from the 4.00 inch bore family. All small block heads have the same bolt pattern.
Not a good idea. 350 heads will lower compression to 7 to 1 or less.
305 heads of course, 350 heads will fit for sure and possibly 400. obviously no big block heads will fit. a 305 with 400 heads gets you a little over 352. 350 with 400 heads is a 383. add and divide