I am going to check out the wrecking yard and was wondering what years vehicles to look for. I am assuming that the 308 is the last 3 numbers in the casting under the valve cover. Anything else to look for?
Thanks

89-92 360 had 308 heads. Trucks and Vans.

Some 308s have the number cast on top of the runner and some have it cast under the runner. The easiest way to identify them if the number is not on top of an intake runner is to look at the port size, they are the same size as any other 360 port opening, if they are indeed 360 heads look for a roller cam, 308s are the only heads on roller cam 360s because the pushrod hole is drilled quite a bit bigger in them than normal 360 heads, that hole is the only other way to identify them if they are bolted on and no cam to look at, other wise you got to pull them to see. You should not buy some with out pulling them first because a lot of them crack.

They are out there, but they are scarce! They were a 360 only head and only for a few years, so not a lot to begin with. If your search comes up empty, probably time to step up to the Magnums. They are a better head anyways. My search started for 308's, but I ended up with Magnums, and I'm glad now it turned out that way.

How much work were the magnum heads to convert to a 340?

if you get maggies complete with the rocker gear, all you need are different pushrods & lifters (maybe even not lifters if you have an aftermarket cam), and intake (or redrill the heads to LA intake bolt pattern). if you go with new aftermarket magnums (enginequests 318A's & 318B's) get the B's, as they're drilled to LA intake pattern. do a search in the "best of" tech archives for magnum conversion for more info.

if looking for 308's, as hotroddave said, look for a TBI injected 360, most likely to be found in 3/4 and 1 ton trucks and vans.

Thanks for the info.