The rear brake line is in the front, as both indicated on the old MC (an F and R are present over their ports) and Wilwood's instructions.

The prop valve and residual valve are in the rear brake line as well, as indicated by the Wilwood instructions, and 10lb because the rears are 9" drums.

I don't quite understand the "gap". Am I measuring from inside the pushrod where it meets the piston, or what?

I still wonder if it was just a product of me having all the pressure to the calipers. Though I don't know why it won't come back out, unless I have it so the pushrod (which is adjustable) is actually pushed in a bit because the rod length is too short?

Thanks for your help guys, and keep the ideas coming.