on my 54, I did this swap. I didn't do it for any "upgrade". As Bill said.... the final gear ratio is the same at 1:1. I swapped motors to a 230 and just did the tranny at the same time. I MAY use my granny gear in the future pulling a small trailer. So I went ahead and did it. Plus, I had it available.
If you're looking for better performance.... skip it and go with something else. If you have the 4 speed readily available for super cheap, go for it. But I would still repair your 3 speed and put that back in... its got the cool factor, and you dont see them much ever anymore.
