[Accelo]

The THM 350 has an length of 21 5/8 in. to where the tail shaft attaches.
The 4L60E has an length of 23 3/8 in. to where the tail shaft attaches.
The 4L60E 1998 and later has an length of 23 3/16 in. to where the tail shaft attaches.

I failed to find the total length of the transmission / transfer combination. Since you have both post the total lengths of each.

With a nominal 2" greater transmission length, you should be fine, but without transfer-case length I can't tell for sure.
Using your current driveshaft length I could calculate the difference in angle. I can't do the maximum angle unless I know the current angle.

Don't forget the new transfer-cases swing both ways and one is a give away price the other expensive. But you likely know that already.

The speedometer going to be analog or digital?
The rear reluctor ring is not always installed in the 4L80e transmission. The basic rule of thumb is 4WD transmissions up to 1996 should have a rear reluctor ring in the main transmission case. The 1997 & newer 4WD 4L80E transmissions had a sensor provision; however, the reluctor ring in the transmission was left out.