The 'jitterbug" is a small orbital sander. Sometimes called a palm sander or random-orbit sander. Basically an electric buzzy thing that'll give a decent finish on the aluminum free of any gouges, lines, or scratches.

I can't believe that any of these solutions is equal to having the head machined however. Cheaper certainly, but how much will it cost to do the job AGAIN?

With this scale of a job you want to do it right the first time.
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Rob Bareiss, New London CT ::: '87 244DL/M47- 234K, '82 245T/M46-182K, '89 244DL/AW70- 212K Not too distant past: 86 244DL 215K, 87 244DL 239K, 88 744GLE 233K, 88 244GL 147K, 91 244 183K