How to move calipers to the rear of spindle?

You have to swap the spindles from side to side. I have them to the rear on my 66, done by accident when I installed the spindles but it don't really matter, just harder to bleed the brakes cause the angle of the bleeder is off.

You have to swap the calipers side to side too to keep the bleeders at the top of the caliper so you can bleed them properly.