Daryl, I have Stewarts 6.2MPI (320hp is it?) in my garage.
I think its done under 100hrs from new, did about 61-62mph in his extreme 24 and id guess a shed load less fuel than your 454!
Complete with the bravo.
I think he's undecided whether to keep the package for the next boat or not, but I could always put an offer to him if you are interested.