After much thought, and judiciously weighing input from this forum and the information I was able to glean from many reloading manuals, and talking at length with the master gunsmith who inspected my rifle and pronounced it to be in extremely good condition. I have formed the following conclusions.
Knowledgeable sources fall into three camps.
Camp 1- It is unsafe to use anything other than black powder in an original rifle.
Camp 2- Original Rifles in good condition can handle smokeless loads up to 28,000 PSI (SAAMI,Hodgdon, Western Powder (Accurate and Ramshot powders), and the Quickload software. My gunsmith is also in this camp.
Camp 3- Original rifles in good condition can handle smokeless loads up to 18,000 PSI/CUP. Lyman and Lee are in this camp.
I have decided to try some smokeless loads using IMR3031 and Accurate 5744 and keep them below 18,000 PSI. I made this choice for two reasons.
1- I have used Goex for many years in my TC Renegade because it always goes bang with the #11 caps I use. Cleanup used to be a minor chore in the kitchen sink. The last time I did this, my wife and granddaughter walked around holding their noses and staring daggers. I now clean it in the cold garage without the benefit of hot water using October Country's cleaning solution. I am also convinced that black powder lays awake at night trying to devise ways to find nooks and crannies to work it's way into, to rust my gun despite by best efforts to clean. Just my experience, YMMV.
2-The velocities I should be able to get at or below 18,000 PSI with the 32 inch barrel are ideal for me and should be close to the velocities I get in the 18 inch barrel of my Henry lever which I load to 23,000 PSI, thus making trajectories very similar. That makes things easy for hunting.
I bought a pound of Black MZ and plan to call Alliant this week for info they might have on using it in the 45-70. I will try it in the Henry then maybe in the Trapdoor if they have actual pressure data on their loads.
When I get recovered from the cataract surgery, I plan a nice long range session with both loads and a chronograph. I will report back.
Thank you all again for your considered replies.
BTW, the "erosion" I was seeing with my bore scope was lead after all. I've got most of it out with copper wool wrapped around a brush.