LS rockers on a Mopar?

I totally agree. You never know when you might hit on something. Just not this time. LOL
Actually, by doing a quick mock-up on it with a set of iron heads and an 1/8 square washer underneath rocker shaft straddling the rocker stand, the geometry looks great (well, considering speedmaster especially!), going by Mike’s (B3) directions. Mock-up on the long block will tell the tale. There might would have to be some grinding for pushrod clearance, but that’s fairly typical.