Need Model 1890 Repair Information|Winchester .22 Rim Fire|Forum|Winchester Collector

I recently required an 1890 in .22 Short and need to make a few repairs. The carrier has been modified to handle a long or long rifle cartridge, the rear sight has been changed out, and one pump slide handle screw thread is messed up. I would like to clean the rifle up and replace or repair what needs fixing. It’s a 1915 rifle and the bore, metal, and wood are in pretty good shape, but it needs to be disassembled and cleaned really well. I’m not sure if the previous owner has re-chambered the barrel for the longer shells, (but I doubt it considering the bad altercation to the carrier), and I probably won’t address that unless the accuracy is really bad.

I’d like to know the thread size of the pump handle screws so I can chase the threads in hopes that they might hold an original screw. And in replacing the carrier what is the best way to remove the small pin that’s in the take down screw..? I can barely see the small pin at the very edge of the retaining pin collar. Is there a chance I can tap down on the collar and get enough room to take the pin out of the take down screw..? Is there some other “trick” to removing the small pin..? Anybody have a guess as to what type of rear sight this is…Marbles 80 Sporting maybe..? There’s a photo of the Marbles on the Homestead website and it looks very much it. It’s unmarked, at least not marked on the top side, but it seems to be well made and in nice condition. 

I’ll try to attach a few photos showing the altered carrier, the retaining pin area, and the rear sight. Thanks for any input or advice, I appreciate the time..!