J Head with new cam caps - good idea?

Picked up a J head with no cam caps for $10 originally to get the valves and shims. I would like to salvage and use the head if possible. Now I know that heads should have their specific set of caps as they are line bored but is there any chance of finding other caps that fit? I have been looking through a few spare caps and I have found four that fit pretty well numbers are not matching and two fit with the arrow in a reverse direction (which also reverses the direction of the slot in the steel bearing)

My question is this...how tight a tolerance in fit should there be and .....does it matter if the arrow on top of the cap is reversed? When I was testing the caps I rejected any that didn't slot easily right onto the two steel locating pins and then any that exhibited even a tiny ridge that my fingernail hung up on (checked all four inside edges)

Many thanks

You could probably find some that work if you had a bunch of extras laying around. I would check them with plastiguage. As far as them being backwards on the arrows. I dont know if that would be a problem or not. The only thing that i could think might cause a problem would be because of the tangs that hold the bearings in. I dont think they would rub the cam, but didnt know it could make them slide or pop out?