1st off, they shouldnt of smoked PERIOD!, which means he didnt do something right, ie; guides and/or seals.
2nd, he didnt elongate the push rod holes enough. Pontiac guys take into consideration max cam profiles that can/will be used.
3rd, if 48 heads are to big, why puting larger valves in the 46 not?
Agree, the cylinder bores should have scallops(think thats what thier called), which can be added, to may full use of added intake flow.