What trans fits 99?

[D13]

99 Sierra 3/4 extended 2wd 5.3 4L60E Trans is starting to go, losing my TCC and some of the shifts are getting soft (150k - don't know why LOL). Looking to swap out the unit in the interest of time. Local J-yards want to sell me ones from 5.7 Vortec vans (apparently they was a rash of wrecks in vans or something). And not being very cooperative about the interchange listing. But isn't the new unit different than the 96-9ish Vortec units? Wouldn't a unit from 4/8/5.3 in 99-2002 be the right one? I'm thinking that while the guts of the trans might be similar, the difference between the Vortec and my high-revving 5.3 (man this thing will go, even in my 5400+ lb truck!) probably calls for different converts, and speed signals, etc.

Anybody know? Thanks!