@mijostyn Thanks for the excellent suggestion. The 698 headshell is made of plastic and is very brittle (bought it in 1977!); I’d be really concerned about fabricating it as you describe. Also, the 698 in original condition is probably worth a fair sum if I were to sell it to a collector.
@lewm The 698 headshell has two captive nuts that receive the connecting screws. Your point is well taken, the nuts could twist during cartridge installation and break the headshell. Thanks for your observations and recommendation.
Given the potential value of the turntable to a collector in stock condition, maybe the best option is to carefully install a new tone arm and put the original aside.