Without MoBo reference it will probally be a guessing game on jumpers. I'm not sure I understand the situation, but if you have onbd AGP graphics, shouldn't you readily discern the mon connection ?
If you have a spare audio bd use it to start with. If you have a dig cam , take a few pics, jpeg them and put them on here, maybe someone can go from there.
Also use a spare graphics bd if you have one, it's not necessary to use the integrated A/V.