The deluxe fresh air heaters from 47 thru 52 appear to me to be different from the 53/54 heaters, in that the nipples on the core are straight across from each other on the early heaters, and have a funny little offset on the 53/54 version. I think that they look identical other than that. Am I right? So, my 53 core leaks. If I can't get it repaired, and I come up with the earlier version, it appears to me that the only issue to installing it in my truck would be blocking one of the holes in the firewall and making a new one to line up with the nipples. Am I right about that??