Oh sorry. It was the 84t spur. My temps were around 140*F. With ambient air in the 70F-80F range.
22/84 gives you a 9.92:1 gear ratio.
22/87 gives you a 10.28:1 gear ratio.
23/87 gives you a 9.83:1 gear ratio.

If you ran the 22/87, it would be a bit cooler. Or you can run the 23/87 and have more top end, but will be a bit hot.
You can start with a 20, run it for 5 minutes and see how it runs and temp it. From there you can go up or down.

You should always keep a few on hand so I would recommend to get a few different sizes. I always have 18-24t pinions on hand.