A few things, I've put swirl port heads from a 318 onto a 360 with a Performer intake and a 340 repro cam. Better mileage and torque than with the stock 79 360 heads. Would I replace magnum heads with the 302'S? No.
Also, drilling the oiling hole in the block so that a Magnum block can run LA heads is no major feat, Chrysler only drilled millions of them over the years, if it's beyond your machine shops ability get a different shop.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
