All chevy distributors fit all the v8s-------small block, big block, tall deck, short deck
You get into those corners or out on the point when you use standard deck manifolds on tall deck blocks, mill block/head decks to adjust piston squish, tall deck manifolds on short blocks, etc--------


The aftermarket manifolds are probably a little bigger to allow for the moving around to line up ports, uneven tightening of bolts, etc---------it is important that the dist lower end fit the block snuggly in that oil gallery and at the proper height for the correct gear mesh with the camgear ---------