Keep in mind that the OEM head gasket may have been .018” thick and your replacement may be .042". You have that difference to remove before you even have to think of the intake alignment.

I cut RB blocks to 10.680” pretty regularly with no problems. I do hit the China walls too though, so there isn't a funky step for the valley tray.

That is something most shops fail to do.

I have a 383 that is cut about .030 and the heads had about .050 off them, I had to take about .075 off the the china walls to get the valley pan to fit right .

Back in the good old days we would cut .040-.045 off our 440 blocks with TRW pistons and stock rods and cranks. That with domed pistons, 750 roller cams, 906 heads, and tunnel rams would push us into the high 9's. Sure is a lot easier now.

I index that surface with the BHj fixture as well. That way, if I'm installing a girdle, I can square the pan rails from the China wall as a reference to mount from. Some of those new cap/girdle kits require cutting the caps and the whole pan rail at once.

It usually takes .030" just to get 'em square. Don't think there's enough material to lose the "champher" ?