Are you saying the new ferrea 5000 1.74’s have about a .060” higher tip height than a ferrea 5000 2.08?

If so, I don’t know that you’ll be able to correct it that much by using a 1.81 valve...... either as a 1.81 on a 1.81 seat or as cut down to a 1.74 with a thick margin.

That’s a lot to make up.

If that’s how far off they are, I’d just cut the seats out and start over.
Not really that big of a deal........unless they installed the super hard seats(Those are a b-yotch to cut out).
Normal “hardened” seats machine easily.