Why is there a concern about Stainless? Brass works very well and lasts. I ran into some re-sleeved years ago and they worked. Have you ever tried working with stainless? Brass is a walk in the park in comparison. I just replaced the original cylinders in my 1950 Mercury due to rust when they finally started to leak last year and due to procrastination in ordering NOS I ended up with China in the front and Italy in the rear. The hoses fit including the mounting bolts but the bleeder needed a metric wrench! If the cast iron lasted this long brass will outlast me. With brass after enlarging the cylinder a piece of brass stock can be pressed in and machined out using a lathe or small milling machine. Heck even pressing in steel would work as well.