Found this after getting the cam out. It's between the lifters of #3. I cant find a corresponding polished spot on the #3 rod to indicate contact. Is there somewhere else I should be looking?

Could be damage from a prior failure, Stew. If you can spin everything and have no interference you likely have evidence of prior rebuild sin. As long as the cam hasn't deformed from the stress I'd say press on.

That's the crux of the matter. Do you know how cam grinders align a camshaft so that all bearing surfaces are where they should be? The hit the side between the lobes ith an air chisel. Quite an art actually, I have watched them give a little buzz, measure, give another hit, maesure and get the cam dead straight.

If the contact with the cam was strong enough to effect the same sort of change in the cast iron shaft, it could have pulled it out of line. It might be a thought to take it to a local grinder and get it checked for true.

Cam is being replaced here in about 20 minutes if I can get off my butt so we will see what happens when the crank is turned. Every thing else look nice so far.

Cam is in and no contact with anything when the engine is rotated so it looks like I dodged a bullet. Now the fun part when the wrenchs turn clockwise.

The rod bolt comes very colse to cam on straight rod MGB engines, that's why they are chamfered on the edges, when using a ARP rod bolt set on straight rod MGBs, you have to chamfer the bolt head yourself for clearence, as the bolt sold for MGB stright rod engines was originally designed for a AMC engine. Though even with stock MGB rod bolts it's really close,lots of things could cause this, a turned bearing in the past would cause the rod to move closer to the cam.
TO answer your question, no I wouldn't worry about it, as long as you have clearence now, you shold be OK, I even seen people put MGB cams on the lathe and turn them down between the lobe in these areas to give clearence.