Well, I guess I am in this club. After being out of the hobby for 8 years or so, I'm getting back into pinball. Currently I have a Lost World and an Embryon (both projects) that qualify me for club inclusion. In the past I've had a few others - Mata Hari, Flight 2000, Space Invaders. And my want list includes a bunch of others - Xenon, Centaur, Catacomb, Fathom, Paragon, Meteor, Medusa, Black Pyramid... Between the machines I've had and those I've worked on for others, I'm pretty good with the solenoid driver boards, the light boards, transformer/rectifier boards, probably will be okay with sound boards. I haven't had great luck in the past with MPUs, but I've got three or four sitting around that had battery corrosion that I hopefully can get at least one good board out of for the Lost World. (I'll probably drop an Alltek into the Embryon.) I plan on picking up a programmer for EPROMs soon (I came across a stash of NOS 2716s at work that were about to be tossed) - any recommendations there? - I'll be using a slow old PC running Windows XP, as I've been running a Mac for a while.
I've ordered some stuff from GPE to get the Lost World up and running, minus the sound card. Don't have the right one, the one that was in the machine when I got it is a -51 with Mystic ROMs installed, and I don't think that works with this.
Anyway, I'll be popping up in here every now and then, and if I start any threads specific to a machine, I'll post a link here.

Replace BR2 on the rectifier board?

Do you have any sign of corrosion anywhere else on the board, particularly along the bottom near the reset section?

I contacted Swinks earlier this year about reproducing this part. I sent him an original to work from, and he finally received it a little over a week ago. So it's in the queue to get done...

And today I got a surprise in the mail:
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And here is one head trimmed from the little connector piece between them:
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I made a quick and dirty jig to support the kicker arm while I pounded out the roll pin and removed the old broken head. Then I put the new head on and pounded the pin back in. (I highly recommend using some sort of similar jig to support the kicker when you're pounding, and use the proper size center punch if you can!)
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And here it is all assembled:
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I sent some pictures and feedback to Swinks, and they are now available here:
https://www.shapeways.com/marketplace?type=product&q=swinksc-1062

Unfortunately, I am just starting a playfield swap, and won't be able to play test these for a while...
That said, the new kicker head seems to fit the same as the original, and I am very, very happy with how this turned out!

The Bally kicker heads have been “out if stock” for some time now. The last time I called in an order to PBR he said they were unavailable.

Yes, he is. I am the person who approached him and asked him to do so. He sent me a pair to test out before he made them available to the public, and I got them a few days ago. They are now available here: https://www.shapeways.com/product/EYDX5QLAU/bally-sling-shot-arm-cover-plastic-c-1062-pair?optionId=156965939&li=shops