Distributor recurve

Here's what I measured with the 1979 springs and governor plate in the 1974 distributor (vacuum line to distributor was disconnected and plugged). Initial timing was 10.5 degrees BTC. I only get 7.7 degrees of mechanical advance, which is all in by 1750 RPM. This doesn't seem right.
Timing BTC vs. RPM-3.png
And here's the vacuum advance chart for the 11.0R vacuum pod. There's no advance until vacuum is about 8 inches, and it maxes out at about 19 degrees advance (above initial) by 14 inches.
Timing BTC vs. Inches applied.png