Paint question

Ok, so I am working on a 71 valiant f7 green. We could only find a formula in one of the three flavors my buddy has. None of which are single stage. How much clear can I mix in to get close? =/>10%? Car is a more door and the passenger fender already doesn’t match. I am cool with close, I’ll blend what I can. My friend at the shop is always weary about experiments, so I can’t get a straight answer.
Thanks