Ld340 vs ld4b

FC7VW9 said
Would the LD4B work on a stroked 318 auto in a 68 barracuda?

That manifold is designed to run on 273's and 318's. It would not be a good choice for a stroker motor. It IS worth some money. I sold a nice one a couple of months ago for $288. Probably enough to buy RPM Air Gap if you shop carefully.