Cam wiped out, what the hell did I do wrong?!?!?

I've got a friend who rebuilt the 360 in his pickup a little more than two years ago. He had heard of all the stories of cam failures so he meticulously followed the installation recommendations for his Brand C cam including their lube, light springs etc. He was very careful with startup procedures too. (He's a extreme detail sort of guy.) An exhaust lobe went south in less than 200 miles.
He picked up a new Brand L cam and was extremely careful (even more so) on installation and startup. It started wiping two lobes shortly after installation. I went over the Saturday after he discovered the problem to help him pull the engine but when I got there he was fuming. He had just stuck a Mopar Performance cam from a built 340 Duster that he had removed in 1979 into his block. As I stood there questioning his mental stability he was removing lifters from a pipe tobacco can and placing them in the bores (I know, and he knows you never put used lifters back if you don't put 'em on the same lobe but here he is doing it!) while continuing to mutter about proving a point. His high tech assembly lube for each lifter was Lubriplate 105. We continued to bolt it together as I continued to protest the resonability of doing so. Just prior to stabbing the oil pump drive he grabbed the drill and priming rod and spun up some oil pressure and visible oil to the rockers. We finished the final assembly and started it that evening. Well, I've been waiting to hear from him about cam failure for a couple of years now. He drives it daily and it's got over 20,000 miles since he stuck in the used cam with mismatched lifters and it runs great.

If someone can say what he did wrong on the first two cams I would be very interested. He says he has proved his point but he won't clearly say just what that point is!