MAGNUM HEADS ON LA
LAs oil the valvetrain through the block, Magnums oil through the lifter/pushrod; so "without resorting to a roller cam"- you'll need oil-through flat tappet lifters (either hydraulic or solid) and custom-length hollow oil-through pushrods.
When selecting the LA cam, remember that they're spec'ed at the LA's 1.5:1 rocker ratio, and Magnums use a 1.6:1 rocker. Adjust the numbers accordingly.
Take into consideration the Magnum's 62cc combustion chamber as opposed to whatever head it's replacing on your unknown LA (you never did say what it was, just "an LA").
You'll need either a Magnum specific intake, or have the Magnum heads redrilled with the LA bolt angle.
Alt/WTR PMP/PS all the same?
As long as they match whichever timing cover you're using, accessories still fit. The heads have no bearing on accessory fitment, everything bolts to the block/wp/tc - the one bolt boss on the head that you'll need is also present on the Magnum head.
And just so you know, LA water pumps (Auminum right side inlet or iron left side inlet) do NOT fit Magnum timing covers, just as Magnum pumps do not fit LA timing covers.
