I agree with Rumblefish360, there is a possible 30 + H.P. increase with magnum heads. Draw back are the head bolts (I would use studs, have to if alum. heads), the R/A gear is close to the same as Chevy and the intake manifolds available are - single plane Mopar Performance or dual plane Mopar Performance or Edelbrock. Engine Quest has magnum heads with magnum R/A, flow better than most other magnum heads and come with either "A" engine intake bolt latout or magnum intake bolt layout; with this you can use the "A" engine layout and use a 6-pak intake, tunnel ram intake or the rare Street Tunnel Ram intake, along with single or dual plane.