I am seriously considering the purchase of stock 99' 502 MPI's for my 89' Formula 272 SR-1.

The original motors are 7.4L 454's. Can anyone tell if the existing brackets and externals will "bolt on" without any mods? What about the stock exhaust manifolds? I have to think that while the blocks are almost identical in exterior dimensions, the hole placement(s) for the externals might be different.

Any advice would be a huge help.

You're going from Gen IV to Gen VI. Not much is going to bolt on. The exhaust should but all you accessories are different.

I know the 502's are Gen VI, not sure what the 89 454 is. Your wiring harness will probably be different. Don't know what else. If the 454's are 89's, I would consider new accessories, belts, hoses, exhaust, etc anyway.

It would be easier if you can find a bobtail 502. That way you get everything new with it and don't have to mess around with aligning brackets or wiring problems.

Bobtails would be way easier, however, cost is always an issue. Anyone have a good source for 502 MPI Bobtails?

there is some used 502 mpi mags for sale in the oso classified ads your best bet tho I think is rebuilding your 454's

I switched from '90 mk iv to gen VI and used my old accs. Had to do very little and mounts were the same,,my Gen VI was a 454 so don't know how diff a 502 would be but I doubt diff mounts. Wiring wouldn't matter unless you want to run new wirng with knock sensor? I'd do it if it was a deal,,it's SOOOOO much fun building brackets and stacking washers
If you change your mind I might want the 502s.

Forget that wiring comment,,MPI ,DUH! Would it come with the ness "brains" for the new mtrs?

All the mounting holes should be the same, but MPI motors reqiure a special wire harness, read expensive. MkIV acc. brackets will fit for power steering/altenator, but you will need a need an electric fuel pump or a seawater/fuel pump combo. The Gen V & VI motors don't have the neseccary boss for the mechanical fuel pump. The 454 exhaust will fit, but I'd prefer something better like Gills if it were mine. Plus you'll want to check the old exhaust to be sure they don't leak before installing. New gaskets and check the mating surfaes between manifold and riser. Good luck, have fun

I would not put stock or used (stock) exhaust on those motors .....