Brad, what I do to prevent boiling fuel is run a Mallry 110 pump at the tank area, 3/8 line to a bypass regulator on the right inner fender by the engine, 3/8 line to the carb, bypass 3/8 line back to the tank which enters near the top of the fuel filler tube. So at idle it is pumping about the same back to the tank as is going towards the engine minus the idle fuel consumed. I also have a Mr Gasket fuel log at the carb and I take a 1/4" line off that back through the original vent line back to the tank pickup unit. That 1/4" line is restricted in the fitting at the fuel log by using a pop rivet (with the mail removed) stuffed inside the fitting. So this gives a recirc of cool fuel virtually to the carb. So on 40 deg C days (thats 100F for you southern dudes) in Salmon Arm I can idle as long as I want. Only thing though is it is a bit finicky after sitting for like 20 minutes in those temperatures at startup and slow running for about a minute until the hot gasoline is expelled back to the tank. I am also contemplating firesleeving the lines where they come parallel to the right side header as that is a large source to pickup heat. So far absolutely no issues running in summer temps.
Hope this helps. Love your casting and yes you picked the best manifold for a 4 barrel setup IMHO.
Barry - and I finally located the literature on the hydraboost setup so will scan it all on Monday week (5th Dec) and send - honest.