Well, gentlemen, it turns out the 507 arm lift is much larger in diameter than the 501 arm lift. I was going to attempt to remove the support body trom the arm, but I would have to disassemble the entire arm. A few years ago I would have done it, but at my age, and stroke-effected body, I chose not to.
I was able to mount the arm lift support assembly in my drill press vise, and clamp the vise down. I then used a 5/8" Forstner bit to drill the hole out to fit the 507 arm lift.
It's a tight fit, but it fits and works beautifully, and it's a great feeling having my arm and turntable working perfectly again. Thank you Dover, for suggesting trying out the 507 arm lift. I'm grateful.
Best regards to all, happy vinyl listening!
Dan