XLR had a Northstar V8. It didn't catch on much.
Previous C4 ZR1 engines had DOHC and 32 valves... but the new C6 ZR1 did not replicate that trait.
And multi-valves via pushrods starts to get problematic, there isn't a lot of room for more pushrods in the same short block length, and compressing two valve springs with the same pushrod means that the pushrod has to be much stronger and more expensive... or risk bending between the cam lifter, and the rocker arm.
Going to overhead cams would probably piss SBC lovers off to no end.