I have a 1998 gen 6 FI 454 with what I believe to be an internal crack in the block (water in oil). I was curious if a gen 5 block would work to put all of the gen 6 acessories and heads on or is there significant differences.

Thanks for your help

Gen VI is a roller motor, Gen V is flat tappet. I use Rollers with a Gen V but I use the Morals with the cross bar.

Yes (sort of) but you wouldn't want to. Crank, pistons, rods, intake, pan, exhaust; yes, heads; kind of, everything else; no.
Without going into too much detail, they only made the Gen V for a short period for a good reason, it was crap. Oil passages were wrong, no decent cooling changes made over the Mk IV, compatibility issues and a generally rushed design / build meant the engine was no good from the start (IMO).
When they released the Gen VI in '96 they called it the 'Gen Fix.'

Go find another Gen VI block, trust me.

Thanks For The Info. I Kinda figured that from doing a little research. Having difficulty locating a gen6 block.