Started with a Bosch ECM case out of a BMW.  This case uses the same Bosch 35 pin main connector as the Weber units does.  This will make swapping the two much easier to accomplish.  There also will be a DB-37 connector out the rear used by the expansions ports.   The barometric sensor will stick out an existing hole on the side of the case. Also will mount an RCA style jack to the rear for the audio output.

This is what we started with.  A Bosch case out of a BMW.
Here the two original PCBs are split open.  All through hole technology here.  A very labor intensive design with all the hand padded resistor stacks.
This is what it looks like with the PCB boards removed.  You can see the convent .5" hole in the side of the case where the barro sensor hose bib will stick out.
Here I have marked where to take off the old features that used to mount the TO3 transistors.  Left enough behind so that the bosses that will hold the new PCB still have some meat around them.
Right side rough cut off the mill. Cleared the extra material around the barro hole also.
Removed the extra material from the outside of the case also around the hole.  This hole originally mounted a large press-in diode.
The other side of the case.  All the extra flashing I will remove with a fine 3M disk to give the TO-220 driver transistors a good flat mounting surface.  The vertical step in the thickness of the wall I will have to work around in the layout.
What it looks like after the mill work.