[jnyeager]

Hey Double-A, you should sell that entire A/C setup as a unit and it will fund all the parts you need to convert to non-air. You can get the non-A/C blower boxes repo, but not the A/C ones. There is a running series of articles in High-Performance Pontiac that is covering the restoration of a 2nd Gen firebird. They are converting this car also. 1 or 2 issues ago, they covered the welding in of some sheet metal to close off the A/C hole.
You can try to modify your existing box to deal with this, but selling it in tact would net you some money (I bought the small half of the box for $40, the whole thing could go for $100.) Of course that doesn't pay for the sheetmetal work you would otherwise need unless you are restoring the whole car anyway.

J.Y.