Slap Stick

If the throw of the shifter is different, logic tells me that you would just need the matching lever for the transmission for it to work. I dont know if the throw is different but the conversion should be pretty straight forward once the shifter is bolted in place.
Most likely you should be able to use all the E body levers, shifter, linkage but may have to shorten the rod. You would want to shorten it at a straight section or else it can change the throw.
Honestlty, I love the stock floor shifter. They work great with my reverse manual valve bodies. I would assume a slapstik would not work with RMVB.