Question about 73-87 Frame Z and Crossmember Mod

I don't know if this can be answered but I have a 74 C10 that I would like to lay pinch weld on, I plan on doing the crossmember mod where you don't raise the motor, and I think I'll do a 2" frame Z, my question is How much did all you guys that Z'ed your frame have to raise the tranny tunnel? I've searched the froum but didn't find much?