Will the parts of a Hi Wall pretty well interchange with those of a Lo Wall?   Specifically, I'd like to take the SST from my Hi Wall and put it on my Lo Wall.   I am assuming that I'd have to switch the hammers as well.  Any thoughts?

George

You'll want to swap individual parts, not the lower tangs.  The swap should work perfectly, if your hammer is cut for the fly.   

The hammers on high walls and low walls are different.  I know a low wall hammer will swap into a high wall and work, just looks strange as it sits lower.  Not sure if the high wall hammer interchanges in, but I can't think why it won't.  Just sits higher so might look odd.

Most hammers are cut for a fly, even if it wasn't installed.

I've installed a few single sets when the parts used to be readily available.  Other than some tuning to make them work well, it was a pretty routine parts swap.

George, if you're on MVAs web site look for "Action Parts" at the top right of your screen.  Click on that and then scroll down and you'll find action parts for three different types of high walls.  I've ordered many parts from them as recently a few weeks ago.

If you have an early low wall with a modified high wall block look at the underside of your trigger.  On thé early high and low walls the trigger often is drilled and tapped for a set screw and has also been drill for the catch hook spring.  In that case, you can order set 
screw, catch hook spring, catch hook, the stronger knock-off spring and as SSDave says, replace those parts in the tang.  Be aware, there will likely be some fine tuning involved.

Wyoming Armory also sells all the 1885 action parts. They have them for the standard trigger, the single set trigger and the double set trigger and their  schematic breaks it downs to which parts are unique to each type of trigger. I’ve bought different parts from them over the years and they are quality made.