I have a fuji sportif that has this fork: FC-770 carbon integrated w/ 1 1/8" alloy steerer

I want to replace it with a steel fork so that I can put a front rack and panniers.

Are these the right forks?

Do I need to measure the length, etc?

You want a fork with mid-fork eyelets so you can mount a lowrider rack. Surly's "Long Haul Trucker" fork is an option.

Someone in C&V was also offering a touring fork up recently that might work for you. Check the ISO and for Trade thread, last page.

Good luck!

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...there are some specific issues that come up with integrated headsets that make choosing a replacement fork a little dodgy.
You may or may not run into issues with the crown race, and I think some of them are integral to the fork. I'm assuming you want to reuse your current headset.

If that's not an issue (it's probably not), then mostly you're looking for a fork that has similar specs for trail and reach (how big a wheel it is designed to take). If you replace it with something with a significantly different trail ( where the tyre patch hits the ground in relation to a straight line dropped along the head tube to the ground ), your bike will handle differently. Might not be too different, and you might like the new handling better, or not.

Generally your best bet is to try for a fork with a similar trail. But there are not a ton of steel fork options out there, so sometimes you have to settle. The steerer part on a new fork is always long, and you'll have to cut it shorter as part of the process.

Of course some bikes have no right fork

Also, you need to consider how much offset ("rake") a fork has, and replace it with a proper replacement. If you change the "trail", it will alter the handling and dynamic stability. If you are planning on doing loaded touring, you don't want too little trail, lest you get instability on fast descents.