GM master cylinder. It looks like a aftermarket Power brake/master unit.A few things that do jump out:
Radiator, rubber fuel line to carb, looks like a GM master cylinder, battery hold down?, ammeter on full discharge
And the convolute tubing behind the vacuum booster.
Looks like it has a new engine wiring harness (a good thing)
I really don't care for the gray but some people like it.