You think the reason the back of the hood had a larger than normal gap was to let the accessive air buildup in the engine compartment a way to relieve itself more efficiently? The sup's are notorious for having poor engine compartment venting at higher speeds. And most extremely fast cars you see have a way to deal with the tendency for the compartment to act as a sail of sorts by catching all the air at high speeds. You can vent it or you can prevent it from comming into the compartment to begin with.

Please note this is just a theory of mine and might not be factual, as i do not know a lot about supra's. This is just an opinion based off of information i have gathered from other race cars in the past.