As everyone else said and what I should have included in my initial response, I would just get reproduction boards. You can even find rebuilt boards for many older Stern SS games if you look, and usually relatively cheap. Quite a few games used the M-100 board. They are all over, and even on eBay frequently. I would get one from a reliable source though, as boards on eBay are commonly "untested" and not guaranteed. Some Bally boards are also interchangeable in older Stern SS games. AS-2518-35, used in games like Mystic and SBM.
And as Barakandl and Ken pointed out, the J3 male pins are shot, so the female connector almost definitely is as well. Given that, the female connector will most likely have to be repinned either way, even if you do get a replacement board. There is most likely corrosion and oxidation inside the connector, judging by what the male pins on the board look like. You should go through and repin every connector if any others are in the condition of J3 or close...just because you'll end up doing it in the foreseeable future anyway. Crappy pins in female connectors just lead to conduction issues Some of the traces on the boards are pretty rough as well, and you don't want to start bridging it with solder, or putting jumpers (hacks) everywhere. Plus your Q54 tip (TIP 102) is probably bad also...that transistor goes bad on practically every old Stern board I've come across. I'd follow Zac's advice, and just keep these for spare parts.