340-360 Head Question?

J heads came with 1.88" (340 & 360) or 2.02" (340 only) intake valves. Later 360 heads (i.e.: 587, 051, 974) all had 1.88" intakes with very similar and flow numbers. Flow would likely be influenced more by the quality of the valve job than the OEM port shape. Some people like the much later 308/576 heads, which is often debated. There are flow # charts online, but often they were not done on the same flow bench, or there may be other unknown influences involved. But they are an interesting reference.

New seats in worn heads or opening up a 1.88" head to 2.02" with a fresh, high valve seat will help, as will stainless nail-head intakes. Exhaust valves are said to like a tulip style head. In my opinion, smoothing out the bowl area and port touch-up would offer the most benefit for least amount of labor after a good valve job.