70 Challenger, manual 11.75 disc w/11" drums.

Upgraded MC to 2-bolt aluminum style with AR adapter plate.
Bleed entire system and switched to DOT5 fluid.

Pedal now does not return high enough at rest to turn off brake lights.
It's about 1/4" shy.

Is there an adjustment to move the switch?

Simple answer, yes. It's fairly easy to reach and pretty obvious once you get under the dash. Shouldn't take you more than a few minutes.

Not sure if you can squeeze out another 1/4" of adjustment there. The adapter means the pushrod is located farther forward (shorter in effect) plus the alum MC MAY have a thicker mounting flange and MAY have a deeper recess in the rear piston "thimble" both of which shorten the pushrod even further. I've run across 2 different lengths of manual pushrods (may be more) & the easy solution might be the MP adjustable one. Loosen the bracket & you'll have your ans in 2 minutes

The switch is mounted on a plate like this. The elongated slot is your adjustment.

http://www.ebay.com/itm/BRAKE-LIGHT-STOP...1-/400594578096

Thanks for the info, I didn't see that initially.
Time for a test drive.......