TH350 or TH400

What transmission came hooked to the back of a 400 SB Chevy the 350 or 400???? I need to replace the seal in the tail section and need to know which one it is. A prompt response is appreciated.

:smokin:
KodiakBear26

crawl under there and LOOK!
modulator on the side //// THM 400
modulator on the back//// THM 350

yep , seen both also depends on yrs etc,