I got it to work finally . . .
I added a few more coil/windings to the inductive sensor clip on my dwell/RPM meter, and set it so the coil was pressed up tight to the spark plug wire. The current must be a lot less through the spark plug wire on the newer machines.
The meter is by "Sun Electric" may be as early as 1970's vintage, probably 1980's.
I got 3800 RPM out of the new machine (Troy Bilt 2410), which is a tad high vs. the engine spec is 3600, I believe, . . . so I tweaked the throttle setting back a bit.
The old Toro (521) was 3800 RPM, and it has been that way forever, so I left it alone