Joel: There's a wrap for that!
Someone on here did that treatment to a 550 Spyder dash insert. My only caveat would be that 356 lower dash is curved under slightly - If you can get the aluminum sheet to follow that curve, you're golden.
Try googling "Engine Turned Wrap" or "Engine Turned Aluminum Wrap" and you should get a bunch of hits. Make a paper template of where you want it to be, cut it out to fit, peel of the backing and stick it on. Easy-Peasy and few, if any, will detect that it's a plastic wrap. Even the later Pontiac Trans-Am dash was a plastic, engine-turned insert.
Here's the first one that popped up: