Ok, I have older 454's in my new to me Chris Cat - 1984.

Are the newer Big Block Chevy's like the Mercury 525's and SC 700's Gen V or Gen VI ?

Which Generation do most High performance builders use now?

Since I have TRS/Speedmaster 2's I have the BW 72C tranny. Is there an issue whith input shafts? did they change the # splines etc?

Wannabe

Since 1996, Merc has been using the Gen 6 for it's 454 and 502 based engines. The really high perf blocks like the HP1000and 1075 I think are Bow Tie blocks. The Gen 6 is a slightly thicker casting than the 5.

The old flywheels may not be compatible. But the drive plate should bolt up OK. The trans splined shaft rides in the drive plate. The bell housing pattern between all are the same, so you should be OK on that too.
I did a similar swap on a chris cat from Mark IV to Gen V. A new flywheel and electric fuel pump were the only modifications required.
As for engine builders, call them and find out what they use. Most 502s will be Gen 5 or 6 since not many Mark iV 502s were made.

Gary

Thanks Guys, I knew this forum was the place to go.

Wannabe