I think the two would be different. The thing that makes a 4wd r151f special is the tail housing so the 2wd version is not good for much. I think the way to convert it would be to get a tail housing from a blown up r150 for cheap and swap it on. You then need an adapter from marlin or inchworm to mount the gear driven case. Do your homework first as I have not done this but it is theoretically possible. You might also need a 23 spline gear set as I'm not sure if they make a 21 spline adapter. In short you are probably better off using the g52 or upgrading to a w56.
Before you scrap the r151f see if it has the lower first gear set. These are getting hard to find and might be worth something to someone.
