[Phil G4SPZ]

Rivets can be drilled out, using a high speed steel twist drill slightly larger than the rivet. Use gentle pressure. The rivet head will usually part company with the rivet body, which can then be pushed out. Tubular rivets can be removed from either end. You can secure the new valveholder with a couple of 6BA bolts, nuts and shakeproof washers.

Before you start, take plenty of photos of the wiring to the pins, and make sure the replacement valveholder has its pins in the same relationship to the fixing flange. You want the pins to be as near as possible to their original locations, or else some wires may not stretch.