So in my mad quest to figure out wether or not I can retain my stock TH400 when I put my 4.3 v-6 has possibly come to an end. I was told that the jeepster TH400 was a BOC transmission. This frustrated me because I found an adapter by JEGS for a BOP transmission to a Chevrolet engine. So I called and talked to four transmission shops and they said that the BOC and the BOP are on and the same. So the adapter will work or so I hope. Hope this helps someone else in their engine quest.