Does a drum to disc conversion increase or decrease wheel offset?

[Josh69]

I have little experience with drum to disc conversions, and the car is not currently in the same city as me, so I can't take measurements. That doesn't mean I can't, or won't before moving forward.

I was hoping that there was some 'uniform' thickness of a typical GM rotor, versus a typical stock F-body 9" GM drum, that alone should yield the difference, and if that doesn't solely account for the change in offset, I wanted to know what does. TonyL hit on the hat thickness, so that helped.

Is it also affected by the hub, or the spindle, is it just in the thickness change due to the rotor hat? That isn't vague to me.....