The 427 and 428 look the same from the top. Intake manifolds are the same and the heads will bolt up to either block. The big diff is in the block and internals. The 427 is a 4 bolt cross drilled block with #2-4 caps having bolts coming from the outside right above the
oil pan. The 428 has a larger stoke crank shaft and a smaller piston. The 428 heads have a diff exhaust port/header bolt pattern also. You can put these heads on either block though. The 427 has 3 head variations also. The low riser, medium riser or the high riser design. They also made Tunnel Port heads, but they take a different looking intake manifold also which is somewhat noticeable right away. I hope this info helps.