Dual port head....valves oversized?

[vwpackrat]

I have a set of dual port heads I was gonna take apart and put in new valve guides. My question is I've notice that all 4 of the outer (exhaust) valves guides for both heads where the vavle guide seats against the head on the rocker arm side the brass guide is a liitle thicker and slightly larger in diamater than the other 2 inner intake valves. Is this a sure sign that they are oversized valve guides? Should they be the same diameter if stock? When you look from the other side (piston side) at the exhaust/intake valve they dont look any different in thk. or diameter. Could it just be that the outer guide diameter where it seats against the head is just a little different in dia.
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62 Convertible Bug
67 Westfalia