I wouldn't bother with the hood height. Wipers probably won't matter either, but they're easy enough to remove. If the tires are in good shape with no cracks, I'd pump them way up for the test. Maybe 70-80 PSI? Mini spares usually have higher rolling resistance and smaller diameter. Taller LRR tires would help gearing. Getting the engine to run lean will help. Full belly pan and get the rear to match the template. Front end is probably OK, but I'd do spats in front of the tires. Can you remove accessory belts? You only need the water pump to drive 60 miles if you have a good, fully-charged battery. Weight reduction if there will be any stop-and-go or hills. Mobil 1 Advance Fuel Economy oil (0w-30, 0w-20, 0w-16). Fill it to the lower mark on the dipstick. Ethanol free regular octane if you can find it. Make sure there's no brake drag. MPGuino to test mods (if you have a good VSS). Trade it for a Geo Metro!
Pick a warm day! And try to run out of gas as you crest a big hill for a long coast!
