[Maricopa]

I'm not aware of any significant advantages of the Kirkham chassis over the ERA chassis.

Well, it's more original in overall design (twin 4" tubes etc) and so it looks more original under the hood. Then there's the standard billet suspension and better overall brakes and shocks, etc.
Still, seems like the savings wouldn't be that great and since the aluminum skin is wrapped and riveted to the 'birdcage' on a Kirkham I can't imagine it would be very easy to attach a 'glass body. Kirkham did make a few but never (to my knowledge) sold them, they ended up upgrading the depositors of the 'glass cars to aluminum.