Do your home work.

I've got an M1 single plane for stock heads and one for W5's. They look identical except for the bolt hole location. I'll admit though I didn't actually try to fit it.

Building an LA engine with "exotic" (well not really) type heads is never easy. They don't bolt together like the Chevies do. You actually have to build them vs assembling them.

BTW I had econo W2's as well. I had to buy new shafts with offset bolt holes and the billet hold down kit but other than that some minor grinding to the sides of the rockers and a couple shim kits got them lined up and working.

In my opinion it was well worth the time, effort and extra money. You'll probably feel the same after you are done. Good luck.

BTW I used 7/16 pushrods and had to grind clearance for the two center exhaust pushrods. Mock assemble and check everything first before you do the final assembly.