Check these out.

The dimensions are all datumed from the trigger pin.

In this case the two surfaces (in the blue bubble) can be:

.620-.005" and .74+.020"

Doin the math leaves you at a slot dimension of .120" to .145".

The other details (in green) are even harder cause they are made from radii. These parts were designed to be made and measured and gauged in such a way where they would play nice with each other and nothing else.

Maybe this helped? Also feel free to check my math. Im cutting and pasting on a work break.

(Drawing from 1937)

Attachment 110533Attachment 110534