Fixed. Changed the sender, and added a little SunPro pressure gauge on a tee at the sender extension. Here's what the mechanical gauge tells me:
Cold start: 55-60psi
Full operating temp, in Drive (450rpm) 17-18psi
Full operating temp, in Park (650rpm) 22psi
1000rpm 35psi
1500rpm 45psi
2000rpm 50-55psi
Dash gauge indicated normal range, very little movement though... I'm glad I got the SunPro gauge!!