What is the difference between the 351W-4v and the 351W-2v? Is that the valves in the heads? I told you, I'm a rock!
The 2v and 4v descriptions are about how many barrels (venturis) the carbs
have. that means in stock form, the engines (which share the same block)
would have differnt intake manifolds to support whichever carb they had,
different compression ratios, differnt cam profiles, and IIRC, slightly
different heads (quench area and valve size differences). Since your engine
isn't stock in that car (or it IS stock but has been converted to a 4bbl
carb) there's no telling what bits are inside it.
The good thing is that if you want to build it up, it really doesn't matter. Pick and choose the parts you want.