99.9% sure it's an 800, just like the one in my '63 Bonneville. The '66 parts catalog says 62-63 are the same part # for the rack, piston, & worm assembly. As for the cooler on yours, I couldn't rightly say. There's no listing for one in the parts book, and I've never seen (unless it was a heavy duty option I'm not finding).
I just had my gearbox rebuilt at powersteering.com (see:
https://www.powersteering.com/powerg...ilds#GMSAGINAW). They offer upgrades from the 20:1 ratio to 16.13:1, 14:1, and 12.7:1. I prefer my 20:1 (truly "Wonder Touch"), as I can spin the wheel with my finger, but to each his own (I wouldn't like 20:1 in my STS-V - LOL).
BTW, I got the extreme detailing package with my gearbox rebuild, including refinishing of my rag joint. Wow, it's beautiful.