You can get the slip yoke kit for the 231 or the 241. They are both 2.72:1 low range unless you can find a 241 from a wrangler rubicon. That one has 4:1 low range but you can get the low range kit for a 231 to make it 4:1. I don't remeber but I thought I read the 241 had a beefier chain and plantery's. You can upgrade the 231 with beefier chain and plantery's from a dodge 231dhd.
http://www.4x4wire.com/jeep/tech/xfer/np231hd03/
Here's that article. I'm sure I screwed up somewhere. Some one will correct me if I'm wrong.

Blacktero: 90 Montero Lwb V6 RS Model. 16" Toyota Alloy Rims, Dual Bouncy's; Gen II Front Rotors & Calipers; Rear LSD

Sraider: 87 Raider 2.6 base. Work yet to be done.