I'd like to replace my Rock Shox Jett C. I now ride only on the road and MUP, so I'd like to go with a rigid fork. The Jett specs are 43mm of travel and an axle to crown height of 424 mm. All the suspension corrected forks I've found say they are to replace forks with 80 mm of travel. If the axle to crown height is in range, will they do? What range of A/C is acceptable?

Try to keep the axle to crown height within 20mm or so. Kona P2 forks are nice, tough and cheap. Carbonium forks are very light and nice.

Thanks. The Kona looks good, but out of stock everywhere. It's hard to find a fork, suspension or rigid to fit this bike. Can I use an 80 mm travel suspension fork?

Given that your fork has an A2c of 424mm, factor in 20mm of sag at 25%, find a fork with an A2C of about 400mm.