you dont HAVE to upgrade to the the 80e, most people will recommend it because the 60e is just a weaker tranny in general. there are plenty of people that run the 60e behind some mean setups, there are just some things you should look into if you go that route. (ie vette servo, trans cooler, tune, etc.) i don't exactly what you would for sure want to do, but i know there are others on here that should chime in with more specifics.
2000 ECSB 5.3L with K&N CAI, true duals with flowmaster 40s, and 200k miles!