Oops...

[athomas]

U can also use quiksteel or similar, putty that hardens, $5 or so at an auto store, quick easy cheap
If u need to that is

This seems like a likely solution.

Not seeing the other side of the rail, I can't determine if the end of the pin is held down or allowed to float in the sear pin groove. If the pin is secure in that it can't move up and down, then it should be fine. You won't need shims or bushings on the side, because the rail is still there on the bottom half of the sear pin. The sear won't be able to move from side to side. If the pin can float up out of the groove, then you will need something to hold it down. You can use JB weld or make an aluminum block that you can bolt down over the left side of the sear pin. You can drill it out after it is fastened down using a drill size that is the same as the size of the sear pin. That way the sear pin will be totally secure.