I have as pair of 525sc's and would like to replace them with naturally aspirated 540's or 572's. Will both of these fit in the same spit as the 454 block? Does the 540 or 572 have different geometry? Will my exhaust manifold work differently? Is a 572 wider? These will go into a 2000 38 lightning.

The difference is tall deck vs regular deck. The 572 is definitely tall deck and you will have to measure if you are side by side. Tailpipes will have to be customized too.

Wannabe

So 540 and 454 blocks are the same??

No, a 454 factory block can't be used for 540cids, but, when using the typical short deck siamese bore block for the 540, External dimensions are, not internal. So yes, put 454 decals on your 540 valve cover or Flame Arrestor and noone will tell the difference.

You can go 580cid in a short deck but is not suggested unless fighting some rule book. Even then....a 4.500" stroke get's interesting.

Not fighting a rule book and do want 540's. Thanks

Just make sure it is a 9.8 block short deck and the external size is the same

Can Make a nice 540 with a short deck

The simple answer is you can make a 540 out of a 9.8 deck height BBC. Talk to an engine builder that is familiar with how to do it and they will explain. Find one that is familiar with marine engines.

Wannabe