Ok... I've looked at some of the nice dual indicator trams for sale, but I
had a hard time buying one that I will only use once in a while. Besides
none of them come with a shaft small enough for the routers I use as
spindles (1/4"). Instead I made a bar with a cut off bolt / pin threaded
into one end to go in the collet, and I threaded a hole on the other to bolt
on a dial indicator. It works, by swinging the spindle back and forth 180
degrees while making adjustments. Its awkward and slow, but it works and
cheap since I already had a dial indicator (couple of them now).

Still when I swap or rebuild spindles It takes a while to get everything
adjusted and shimmed just right again. (My second mount I made adjustable
so its faster, but still slow.) I was thinking about this, and suddenly it
came to me. I have two good dial indicators. I can make a simple dual
indicator tram the same way as my cheap single indicator tram bar. I don't
need to get both indicators set at exactly the same height. I just need to
get them within 1/4 to 1/2 a revolution or so, and then set the pointer to
zero on both at the same point on the table. I'm not measuring distance.
I'm measuring relative distance. It will make tramming spindles a lot
faster, and I still don't need a dedicated tool for it. The bar, pin, etc.
None of it needs to be made to any high degree of precision.

DOH! I should have thought of that a long time ago.