Yes, I have one on my TR3.
During the 'up-grade' I removed the pulley and installed a wide pulley from a generator. After a few thousand miles, I realized the reason for the key in the shaft of the generator. The pulley spun into the housing and overheated the bearing and threw the belt. Then, I used a dremel and cut-off-wheel to add a key-way to the shaft, and several several thousand miles later, the same alternator is working fine. -If you stick with the narrow pulley, you'll probably be ok, but if you want to use the wide pulley, you should add a key so the pulley can't spin on the shaft.
I also had to use a different size belt. The spacers for the cross bolt can be a little challenging. -And I removed the guts, re-clocked the output wires to be away from the manifold and painted the case black so it's less obvious. I recall slightly drilling out the bolt holes to the nearest non-metric size (and using grade 8 bolts). Here's a picture of the replacement spacer made from a front-end sleeve and washer.