340/360 head on a 360 magnum

Kern Dog said

First off, this isn't a GM engine. The iron used in Mopar blocks has a higher nickel content so the blocks don't have to be bored over as often as a GM block. I've taken apart Chevys at 50,000 miles that had a lot of wear and RV 440s with 80,000 miles that just needed a hone job....the stock pistons were reused with new rings.
Secondly, when you bore an engine too far, the cylinders will actually flex some and that will affect how well the piston ring seal in the bores. Going .060 over to gain a few cubic inches has been found to be a bad idea because whatever gains you might see with the extra cubic inches will be LOST to poor cylinder sealing.

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Some cylinder walls can supposedly be thicker, so if still interested have machine shop sonic test walls for exactly how thick to determine how big you can bore an individual block.
Poly-head blocks weigh more,v but i don't know if cylinder walls are thicker or weight is elsewhere( thicker main webs might be nice for all out build)
And find a machine shop that Knows Mopar & Not just big blocks. Ask.
And can't stock rockers be drilled & deburred to oil through pushrods. That has to be better than any rockers with Needle Bearings.
Bushed ones now are available as people tired of needles failing & trashing complete engines, wearing shafts funny, etc.
Been seeing that dumass idea junk engines in sprint cars since the late '70s. Not sure when bushings started being used replacing them, and should cost less, but don't seem to.
Racing engines are rebuilt a lot more often & they work ok, but I'd bet the rockers get inspected between races, or if not, after several races, regularly.