OK, what I would do is this enter the following settings whilst using VGA

Horizontal total active 1280
Horizontal front porch 048
Horizontal sync width 112
Horizontal back porch 248
Vertical refresh rate 59.94Hz
Vertical lines 768
Vertical front porch 001
Vertical sync width 003
Vertical back porch 030

The with the checkerboard pattern adjust the H and V size until it snaps into place, it should become obvious when it happens.
This will then be pixel mapped and you will be bypassing the screens internal scaler.
Worth trying it over HDMI too, you may find that 1280x768 is so close to 720p it allows it.
Adjusting the screens H and V size is the most important thing to do though, and you will have to adjust thee position on the screen too when you are done to get it central.

No Darling, I've had it months!