I've used the Wilson reversion 1.5 inch spacer on all my stroker 400 motors with both the Indy 400-3 early and late intakes, none of them had the interior work done like yours is now.
I have seen 150 degree difference in the EGT on #2 and #7 cylinder on several Indy 440-3 and maybe one stock late model 400-3 with no spacer on two different brand engine dynos
I had Bob George racing modified one 400-3 intake for me but I don't remember now if it was a early or late model casting or not now