tune before the trans and gear

[sroach20]

ive got a 99 ecswb 5.3. i have an exhaust with headers , 3.42s and some other things. I am getting a trans built up with lots of goodies, along with a stall, and im installing an eaton with 3.73s. i am also going to eliminate that pos egr system. i want to get a nelson tune with some tm removed but i would like it before i put everything in, mainly to keep the tm from screwing up my tranny. if i get the tune and install it with my stock pos slipping tranny will it hurt anything? also what is the highest octane i could run with a stock thermostat?

[GMCwantsLS1]

If you don't change the thermostat your engine might ping with the added timing and higher coolent temps even with high octane(higher octane will resist preignition ping better). With all TM removed it might kill your slipping tranny that much faster. You might at least want to get the thermostat replaces with a cooler one. If you were to go real easy on your tranny it might last with all TM removed until you get a built one.