Re: Fresh Air Intake
first, no wonder the parts rusted - the way they designed it. i would just fabicate some new parts if i couldnt find some in a scrapyard.
second - you can easily make up a metal flap and put something like rubber tubing around the edge. if i were making one of those, i would have it pivot in the center on a rod that was welded to it, with an arm on the outside so that something like a car universal choke cable that you push in and out would open and close it. that would be the simple way.. was the way that cars like my 49 chevy car had the vents open under the dash.
course you could get fancy and use electric solinoid or actuator, etc for the control.
Jesus Christ... Conversion in progress.