The head I am working on now, the Autolite 404's compression ring comes no where near to seating. The clearance hole is too small. So there is a 5/8" still that show be the right one to use? Any part numbers? I usually have to give my local parts guy a specific year for a part in order to locate it.
The other head I was referencing with the super skinny plugs used a smaller diameter thread size and i used a deep 17mm socket to get it out. Those plugs won't fit the other head what-so-ever.
