One of the advantages of the QJet is sheer numbers. If you've got any salvage/wrecking yards around that have "old" cars, you can probably find one that will bolt right in. Take the top off yours before you send it in and make a note of which jets, primary rods, and secondary rods it has (grab a copy of Cliff's book for reference), then set up your "temporary" carb with the same jets and rods (or as close as you can get) - and you'll be fine for just tooling around. Look on old Pontiacs first, as QJets on them will have "front entry" fuel lines like yours (most chevys have "side entry" fuel lines). Don't worry about finding a carb with a specific "number" on it since you're going to be changing jets and rods anyway. However, if you can find one off an engine that's close to yours in displacement (Pontiac 389 and up... Buick 400 and up ... Olds 403 and up... etc.) you might be able to run it as is.
It's not going to be perfectly dialed in for your car, and you might have to run it with the choke disconnected ---- but you'll be able to drive the car.