Before the fire, the tach was reading incorrectly on mine. It was reading 2x the actual RPM. I had also replaced the speed sensor because it was a cheap part, but it didn't affect it. After the cluster became a molten pile of plastic, it really didn't work well at all. If you're getting intermittent readings, check for bad grounds, especially near the back of the engine on the right side (I now know this model really well for some reason, lol).
The replacement cluster was slightly different, it seems like it's for a newer tractor. However, everything works properly. The lights will provide some power to the cluster and make it boot, which is a little strange. It's an expensive part, so it's easier to just live with a bad tach unless you really want to fix it. The service manual is really good, I have it as well.
I'll definitely get an extinguisher to mount.
The 512 is a good loader for this tractor. The only downside is that it uses the JD-style, and my 5055 uses the global style attachment. The tractor is really light and bouncy in the front without it.