[MOTORHEAD]

Having driven many fiberglass and one aluminum cobra (mine) a few differences come to mind:
Fiberglass tends to absorb some of the road and mechanical noise.
It also seems to insulate the cockpit from heat better than metal.
When pranged, it's easy to find a body repairman, or DIY.

Aluminum used by Kirkhams is thicker and tougher (tempered) than the originals, and will stand up to moderate abuse.
It transmitts more road,mechanical, and body noise.
It also absorbs and transmitts heat (something al is noted for) and here in Fl, driving the car on hot days (90+ deg) is like driving an OVEN !!!! The whole car gets hot!!!
Last trip, I had to wait till it cooled down befor I could touch the hood and prop rod !!!

But, I still love it ! there are things that can be done with al that can't be done with fg, like the very small rolling of the fender openings, door and hood edges, that make Kirkhams works of art !