496 HO is very reliable and turn key in stock form. Plus a pair of very good used ones would be a lot cheaper that 500 or 525s.

I understand what you are trying to do. Your engines while great in there day are now tired and maybe even becoming less reliable. I think all three 496ho, 500 efi, and 525 efi are great choices and upgrades over what you have. The closed cooling of the 525 and 496 would interest me if I were you. Ive also never known of anyone having a whole lot of trouble with there 496. Maybe a little something here and there but that boating if you ask me. If you are serious about spending the money then do some homework and look for good deal in the classified's. Sometimes you get lucky and pick up a good pair of reliable engines.

There is a pair of 496 mag ho's in the swap shop now.

Why don't you just buy a 502 long block and put all your stuff on it? Wouldn't that be pretty cheap?