Is this the best fork to convert to 650b? Any other forks I should consider? I have a road bike I really like, but don't ride anymore because it will barely take a 700x27mm tire.

Crust Spark Rando fork: https://crustbikes.com/collections/f...blrFsdePyOtA8Q

Requirements:
- 1" steerer tube
- Lugged steel strongly preferred
- Cantilever or centerpull brake braze-ons for 650b rim
- High rake for low trail
- As light/flexible as possible

The only other one that seems to fit the bill is the Soma Champs Élysées, but it's been out of stock forever.

Looks like the Crust fork checks your boxes. I won't go into what's "best"... Andy (who makes his own forks too)

OK, front tire clearance would go up. What about the rear clearances?

Well, yeah, a custom fork would be better. But also lot more expensive. I guess I should've said "best production fork."

The rear will fit a 650b x 38mm

"Well, yeah, a custom fork would be better. But also lot more expensive. I guess I should've said "best production fork." " FastJake

My focus wasn't on custom VS production. Instead a poor attempt to question how one decides what's best. Most expensive? Lightest? Pretty? joining methods? Presence of lug like shorelines? Strongest? Stiffest or most shock absorbing? I suggest there is no one fork that we all would agree on in just about every listed category. Andy

I'd like to think you're not being deliberately difficult.

Let me try again... I have only identified ONE fork currently available that meets my basic criteria: 1" steerer with canti or centerpull posts for 650b wheels. Are there any others? I will make my own decision on which to purchase.

Why not use your current fork with an appropriate double pivot brake?

I don't have any alternative forks for you. 650b with cantis and 1" is not a common set up.

I will use a small front rack + handlebar bag. A caliper brake uses the hole needed to mount the rack.