I finally got around to rebuilding my 47 EL that blew a cylinder a little while back. Upon disassembly I discovered the front head contained two exhaust guides (no chamfer) and the rear head had the two intake guides (chamfered). Only the rear exhaust valve guide showed wear. These are bronze lined cast iron guides from Manley used with their SS valves which were installed during the last rebuild about 25 yrs ago. I ordered a replacement stock cast iron exhaust guide since I can no longer locate the Manley guides. The guide I received has a chamfer (intake), but is otherwise dimensionally identical to the exhaust guide although I can't verify the stock ID. What is different between the guides besides the chamfer? If I am reaming after installation does it matter? Thanks in advance.