If the heads are off the car now, I would look at them real close. I am 99% sure all 461's were straight plug heads, but there were machine shops in the 70's and 80's that would plug the straight hole, and drill and tap the angled plug. There was a thread on here, or speedtalk from someone looking for the plugs. I think the only older GM angle plug heads were the "292" turbo heads, that were bought over the counter.