I have a 1990 GMC Sierra with a 305, I need to put a new engine in it and would prefer going back with a 350. Can I Put any GM 350 in it from the 90's?

Going out on a limb here..... "Crate" engines are sold with the ECM and mass air flow sensor, so I'd guess that as long as the engine you picked up also had the ECM and mass air flow sensor, it should work.

Let me rephrase, I shouldn't of said new, I mean finding a running used engine. When I said new I meant more of new for me, haha.

And as I wrote "....that as long as the engine you picked up also had the ECM and mass air flow sensor, it should work. " Translation... make sure the engine you pick up also has the ECM and mass air flow sensor