Actually, a 455 is lighter than a 350 because more of the engine is filled with hot air .... right? Since all Pontiac V-8s (should we count the 301?) have the same external dimensions, there is essentially no difference in weight. The crank with its bigger journals and longer stroke will be slightly heavier, the pistons being shorter are lighter, the block with the bigger bores is... only .030" bigger so it doesn't matter. You can put a later (70-79) block into an early car (67-69) but not the other way around. The later blocks have both sets of motor mount holes (early and late) while the earlier blocks only have the early set. Since 455's are from 70-76 you can bolt one of these into your bird with no mods.
