[MARKDTN]

I would not build the 307. It will cost same or more than a 350 with no benefit. It is hard to beat a crate 350 for price. Nothing wrong with a used one for the right price, but I would want to get a 1-pc seal one ('87 up). They don't leak like the 2-piece ones do. With that you would need another intake as the heads for these have the 2 center bolts at a different angle. While it is out I would put a front seal in an automatic trans or a clutch in a manual unless they are very recent. So to me the crate 350 is the way to go. Do be sure you look at the pilot bushing in the back of the crank and take it out if you have an automatic.