Joe in denver there are not many engines I can put in a BII that would not pass the sniffer test set for a 88 2.9L, meaning even a 350 Chevy built to the hilt with a carb would probably pass the 2.9L emissions gas limits if it was tuned well....
For my 88 BII all Denver cared about was a cat converter and that it passed the sniffer test, my 5.0L OBD-II blew lower numbers then my 93 4.0L with bolt ons and a hallow cat, both of them passed, they never seemed to care what was under the hood as long as the stuff coming out the back was clean and the gas cap held pressure.
I know it changing in 07 even better but you still have to pass the sniffer test = no problem as long as its not running rich
My BII is 13 months away from classic plates, I cant wait! Shes also just passed 291K miles