I need to replace my carbon fork and want to go with a steel one.

Mine: A to C is 388. Rake is 40mm. 57mm brakes.

IRD makes a couple but they don't exactly match.

They both have a A to C of 385. The lugged has a 43 mm rake and the unicrown, 40.

I prefer the lugged but how much difference does 3mm in rake make and is a 3mm difference in A to C also a deal killer?

Really appreciate your advice.

3mm in blade length might drop the front of the bike slightly, adding a minute or two (fractions of a degree) to your head angle, but not enough to significantly alter the handling or ride. It also might limit the size of tire you can fit under there, so if you're thinking of running 700x35, you might need to scale back to 700x28.

3 mm of rake isn't going to drastically alter the handling of the bike. If anything, you might notice the extra rake giving you slightly lighter, more nimble steering and increased stability over bad road--sand, puddles, cobbles, gravel, etc.

Unless I was trying to pinch pennies, I'd favor the lugged fork too.