454 mpi question
 

I have twin 454 MPIs in my 2000 29 Outlaw my question is will the heads off of a mag fit, and what if any other changes will need to be made. Or would it just be better to have the stock heads reworked. I know that the heads I have are oval port. I am wondering if I redo my heads and have the exhaust match ported if I can get some more power out of her without having to redo the lowerend. I also have been told to just spent the money and buy the performer RPM heads but I dont think my stock exhaust will bolt up.

WOW! I guess no one knows

Are your engines 310HP 7.4MPI ?
If so, you can not just bolt on rectanglar port heads with 119cc chambers and make more power. They will bolt up, but you will be lowering the CR from 9:1 to 8:1 and make even less power.
Also, the GM oval port MPI intake will not match rectangular port heads.
If you want to make more power with those engines I would make the following suggestions:
First, buy a good breathing set of aluminum exhaust manifold, ie. Stainless Marine.
If you feel the need to go deeper, pull the L-29 heads and have them bowl ported, valve job, and install a set of new springs, retainers, and locks.
Buy a couple of Gen VI 454/502Mag roller cams from an OSO guy upgrading his Mags with a larger.
Last, have Tyler Crockett recalibrate you ECUs for the new combo.
The engines with new cams, exhaust, ported heads, and recal will make 375HP.