Trans-dapt used to make a heat/spacer kit for square flange carbs. It had small aluminum spacers alternated with gaskets. The top spacer was very large and nearly went to the valve covers on a 340 I had. This helped the boiling on the 750 carter comp carb I had. Aluminum dissipates heat better than steel although not as well and phenolic or wood. I'm not nitpicking here, but whats the longetivity of a wood spacer? I dont think plywood would work, id be afraid with would fall apart due to the heat and possible gas contamination. Perhaps hardwood? Ive also thought about underhood temps being a problem on any engine no matter the size of compartment. I was thinking of going to a junk yard and removing two of the louvered vents from the hood of one or two mopar fwd turbo cars and installing them in the hood of my truck. they could be positioned over the hottest parts of the engine, being that heat rises, this should theoretically lower underhood temps. A heat gun could tell you the hot spts, but clearly, hedders would be very hot. They were installed on the first generation of turbo cars right above the turbo. Makes sense at any rate.