I'm buildin a 73 350 for the z. the 350's heads are believed to be 1.72 intake and I believe all standard model 305's had 1.84 intakes, should I use the 305 heads on the build for the 350?

 

Intake valves are generally larger than exhaust, so your numbers are off.

The size of the valve has little to do with which head to use, as long as the valves are not larger than the cylinder. What you need to know is compression ratios, not valve sizes.

 

I think he just said his 350 intake valve is 1.72 inches, and his 305 intake valve is 1.84.... No mention of exhaust valve size in there.

Any 70s 350 head is total garbage, especially if it has a 1.72 inch intake valve. If your 305 is an 86 it's not an HO, but ignoring that, it's still likely got 416 heads which are.... okay for 305 heads. Still far better than any 70s 350 head. If you refuse to buy new heads, I would get the 416's cut for larger valves (1.94 intake at least, 1.60 exh) and put bigger valves in them. But valves are expensive. Cheaper to buy another set of heads. Some bone stock L98 heads are going to be better than either of those options. The L98 heads have I think 1.94/1.5 intake and exhaust valves and they're 64cc chambers which are far better than the smogger type chambers that are probably on your 73.

If you want to branch out a little, you can always get some aluminum GM 113 heads (what they use on the ZZ4 and late 80s Corvette L98s).

But if you refuse to do any work or buy any heads, the 416's are going to be the better choice, but you'll need to get some dished pistons to keep the compression ratio tolerable.

 

I wouldn't be able to just throw the 305 heads right on it? the comp ratio for the 305 was 9-1 or 9.5-1, believe it's 9-1. what would the ratio end up becoming?