I believe the most useful Armstrong lathe holders would be those that don't have a built in angle (the cutter is held parallel to the base). These would include T-0-L, T-0-R, T-0-S, XX-0-L, XX-0-R, XX-0-S. The shaper specific holders that should work are "Extension Shaper Tool #46" for internal work and probably the most useful of all "Planer and Shaper Tool #39". These last two are probably the most useful and the hardest to find without taking out a second mortgage. There is a web page that shows a homemade version of the #39 (Try Googling "metal shapers Kay Fisher"). I vaguely remember it being taboo to share that content directly here.