Valve lapping questions

It will run just fine as-is. Wider seat faces will impact longevity a little. Wider seat faces plus loose valve guide clearance will impact longevity a lot. If I was looking to get something on the road I wouldn't hesitate for a minute. If it needed to run 100K miles before the next valve job, well... The problem is, without installing insert seats you'll end up sinking the valves to narrow the seating surface, and that causes it's own set of issues. I've driven worse, and sold far worse.