Originally Posted by Just1MoreDave 
The lens should have an auto/manual switch. Set it to Auto and the lens will always be wide open regardless of aperture ring setting. Set the camera on Av. You can then focus wide open with the lens if you want. Then switch the lens to Manual. The aperture will now change by moving the aperture ring, and the light meter will see the changes as you make them. So it acts kind of like it should. Exposure compensation works too. Metering switches to center-weighted automatically if it was on multi-segment.
As the Kingfish was fond of saying....'Scuse me for protrudin'....but why bother with the auto/manual switch at all? Just leave it set on manual, open up to focus, close down to shoot. All you have to do is count aperture ring clicks. Easy as pie.
Regarding worries about 20 year old lenses.....I generally carry nothing but lenses
twice that old and use them daily. One nice benefit in addition to their great image quality and ruggedness is that I am able to share lenses between my 5 month old K20D and my 46 year old SV.