Didnt K&B and now RJL mecoa offer 2 piston/cylinder types , 1 iron/steel and the othe being ABC , check the parts availability on Meco's website.
Stewart
https://shop.mecoa.com/shopdisplayproducts.asp?id=105 , I also note that all parts for the conquest didnt interchange between Cox production and the K&B/RJL version