I used a 1750 RPM motor on 3 step pulley jack shaft for years. The day I bought a variable speed setup, I kicked myself for not having done so sooner. It really is a game changer, and you'll find yourself using the full range of speeds for anything from sharpening and finish work, up to full on hogging. What's really nice, is that VFDs are cheaper than ever, and I've seen up to 2hp VFDs from China for around $60. I see up to 2hp 3 phase motors for sale for anywhere from $50 to $150 all day long. So, you could potentially have a pretty nice variable speed set up for well under $200, give or take a bit of wiring, and maybe some filter sheets to keep the metal dust out.
If I had to start all over from scratch, there's no way I wouldn't put a VFD on my grinder anymore.