I have decreased the depth of the rings by carefully using a belt sander.
http://www.classicparts.com/1934-53...216-235/productinfo/89-305/#.VrdfYpMrKdE (for 216s and pre-1954 235s)
http://www.classicparts.com/1954-62...Sleeves/productinfo/89-306/#.Vrdf75MrKdE (for 1954-1953 235s/261s)
Larrow & Sons use to make sell those port-size-adapters (but their web catalog is not working). Jim Carter used to sell them, but they do not seem be listed now.
If you find them listed on-line, please post links
You do not need the alignment rings to make a good seal, but is very hard to correctly align the manifolds assembly to the head without the rings.
