Nicht geblowen die tranny. Don't expect to anywho. CO, one thing to keep in mind, there are practically no internal differences between your R150 and your proposed R151. So your upgrade would be... expensive, that's about it.

My article on overhauling the R151 is the very same process (and very same rebuild kit FWIW) for the R150. The reasons I went with the R151 are as follows:
1) would bolt up to the 22RE I had, as well as the tcase. In case I never went with the 3.4, it was worthwhile by itself, since my W56 was getting crunchy.
2) lower first gear. Not really needed with the 3.4, a nice-to-have, but not needed.
3) It was fun to do... <img src="/forums/images/graemlins/zombie.gif" alt="" /> <img src="/forums/images/graemlins/notooth.gif" alt="" />

Replace the shifter seat, Brian beat me to the punch. If that doesn't do it, throw some Redline MT90 in there. IF that still doesn't do it, tear down the tranny with your service manual and my article. I have a couple home-made tools that will make it easier, that you may borrow. Email me if needed.

If you want a geared tcase, use Marlin's V6 adapter kit. Try to find a 23 spline tcase (good luck), convert the tcase you do find ($$$), or buy a rebuild from Marlin. You will have to lengthen the front driveshaft and shorten the rear, I recommend Englewood Driveshaft locally.

Stay away from that Mark fella, he has very expensive tastes... <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/lol.gif" alt="" />