Had a 96 Gen V 454 in first boat Indmar marine, 4 bolt main, peanut port, NON adjustable valve train, not big cam friendly as is, (ask me how I know  ) 1 piece rear main.  I swapped to 781's. Had a Gen VI 454 after that, had a 6-bolt timing cover, plastic, used a gmpp aluminum one. '99 MIGHT be roller cam already.
8100? I dont know. Longer stroke (4.375"?), unsure of bore.

I have a 99 454 and was wondering if anyone has ran one in a jet.. I also know of a 8.1 for pretty cheap.. What all do I have to do to run one of these???

Headers, intake & carb, dizzy, electric fuel pump, water pump block-off plates, motor plates, typical marine stuff OR use the EFI

Thats all I know

Daniel
Mash on it

On the 8.1 ive found a dart carb intake and has dis. hole.. Friend has one in he's 3500 and says its nothing different the the old 496 with vortec heads?? But!! Yeah.. Bolting headers. Bell. The little things.. I can get the 8.1 for $750 it has 50,000 on it.. Intake is $575