If true you answered your own question... the 4l60e is the limit.Truth man. I don't know much about this rig other than my dad bought it for my mom in 2008, she babied it until now. Has the tow package on it, I'm curious what the limits are to this thing. I'm sure it's a 4L60 trans.
Inline engines are generally longer lasting outside of abuse and defects, and, in my experience, keep on functioning somewhat serviceable in nature even as compression fails and other maladies strike.
They may not run great when broken, but they rarely leave you at the side of the road either.
Consider it a 300k mile platform, aside from that 4l60