I just saw this and I don't think it's all that clear what your talking about - I think I got it figured out, a better description might have helped. For those who don't know what a 75-A is, it's a STEVENS Model 75-A, based on of the Savage 29-A pump 22. It was made for Spiegel and could be ordered with a Mossberg scope attached, the barrels were all drilled & tapped for scope blocks.

Jack First has the stops, you would need to make the small pin - https://jack-first-gun-parts.myshopi...op-223-29a-301

Cheaper one on eBay - https://www.ebay.com/itm/174508111726