Good idea getting rid of the split rims. Some are safe, some are not, but they are all a pain in the keester. Nice that you found some that fit.
Your 235 ought to be happier running at slightly higher rpm than an old 216 babbit.
I thought about turning around my brownie and running it backwards. Assuming you can mount it that way reasonably, AND find a way to make the linkage work smoothly, what's it going to give you? Mine is 2.3, 1.2, 1, 0.8. The 1:1 is the same in both directions. The 0.8:1 is about 1.2:1 in revers and the 1.2:1 is about 0.8:1 in reverse (nothing gained). However that 2.3 in reverse is... well it's TOOOO MUCH overdrive (unless I wanna take it to the salt flats... fastest 58 tonner in the world!). So I can't tell if your 2 speed gearbox will be good or not backwards unless I know the ratio is. Get it? Also, are there any "directional" items in the box (i.e. gear cut, lube pump, etc...)?
I found a 4.10 ratio differential carrier to get more speed from mine. Add to that my auxiliary gearing and I'll still have a lower lo than stock, but I'll also have a higher hi.
