I wouldn't waste time or effort on the used cam for the other engine but that me .

I don't know how trusting you are but unless the guy will stand behind it till you have it running I would be leary of taking his word that it's ok. I passed on an engine that someone used that line on , it came with a taillight warranty , once my taillights were out of his sight so was any warranty . Good thing I did , I ran into the person that did end up buying it and it turned out to need to be bored and rebuilt, he salvaged very little from it and got nothing back from the seller.