Does anybody know if there is a crate engine or any type of engine that can upgrade a 1993 Bonneville SSei current engine?

Well, what goals are you looking for as far as power goes? Alot of mods can be done to your current L67, and even more if you swapped in a Series II.

I believe you could order a crated Series II L67. The engine/tranny combo will be tricky (PCM speaking), though, as the Series II was never put on the 93 version of the 4T60-E that you have. But the Series II has a MUCH larger aftermarket base, and has 35 hp more to begin with.