3200 volts? I was just going by datsun66's post about 2100 which I admit I thought was quite low for 3-500Z's. I wonder if the taps are set right or there is problem's with the filter caps.
If I had to guess I would say it is the resistors in the metering circuit out of tolerance maybe. 35 plus years old resistors may be causing error reading the voltage.
Found the manual on bama website to see what the B+ was, Henry is famous for their CCS PS and high B+.