I think it would be th400.
If you can get pic of the trans pan, could verify.
But 4l80 came out 91 iirc so it could be that.
G vans were all over the place on different parts.
For a 6.2 in a van I believe it will be a 700r4/4l60. The 4l80e typically only came in 8 lug trucks, the 454ss, and 6.5 turbos, but being a G30, it is 8 lug, so it may be a 4l80e. You'll have to look at the pan to see. Not many 6.2's got a 4l80e though.