My time is limited but I might be able to get some answers for him if he comes back.

Seems to me his best shot is to just dremel the space on the side for the side bolt release sear to fit in the stock. That will be easier and cheaper than getting the bottom release sear. In the other hand that might affect the resell price of the stock where I think the sear will be a clean swapp with no mods...

When I converted mine I used a boyd stock that is built for side release bolt in a short action. I first wanted to make sure the action would fit in with the bottom release bolt sear just in case and I had to clear quite a bit of wood. Then I swapped the sear to the side release sear and still had to clear a bit on the side because the inletting is not the same but it was minor. I will look when I can and see how that action will fit in the original bottom release stock and give some general feedback...