Funny that you should mention the issue of the hood insulator pad! When HOT ROD was testing their 1968 Road Runner 383, after their "CAR OF THE YEAR" award, they were at the drag strip seeing how they might make it run faster. Timing, tire pressures, starting line techniques, etc. For one set of runs they took the air cleaner completely off. As they related, before they got to the end of the 1/4 mile, the car stopped pulling for no apparent reason at all. When they raised the hood to investigate, they found the carb clogged with the fiberglass material from the hood insulator pad. Once they got it all cleaned up, they re-installed the base plate with a bar across the top to keep any further issues with the remains of the hood pad restricting air flow. And their "play" continued.
In prior model years, the lh breather was the open "hogs hair" mesh. Usually they would drip slightly, resulting in a burn mark on the top of the exhaust manifold right under it. As it did on our '66 Newport. The more-emissions-control oriented model years used a tube from the air cleaner body as their crankcase air source. That way, any vapors the pcv system didn't scavenge from the crankcase, would be funneled into the air cleaner body to get introduced into the carb's intake air stream that way, to be burned rather than to dissipate into the underhood air environment. Like during heavy throttle application periods when manifold vacuum is low.
Enjoy!
CBODY67