Steven,
First thanks for putting my car in your mag!
Second, yes there is a shoulder belt attach point in the roof, likely hidden as you said by a new headliner.
The belt is in fact adjustable, and it clips into the lap belt latch.
I removed my OEM seat belts after installing my roll bar and 5 point harness, but here is a pic of the hole in the headliner where the shoulder harness attaches.
Hope this helps!

[addsig]