Thanks mosesburb, some good advice there.
Here's a page from my Automobile Guide printed in 1972 which describes the basics of the kind of system I was envisioning (perhaps a bit primitive by today's standards).
I'd think that it would work, but that it would probably be a good idea to plumb a valve inline that only opened above a certain pressure. My Fuel & Emissions supplement is on the way now, so I'll have a better idea of the overall scheme of things soon.
In the meantime I mounted the ECM securely today with a couple of small brackets that are mostly out of sight. It now hangs snugly above the new fuse panel.