If you really think it's boiling the fuel in the bowls you might try a heat shield under the carb. Several of the BB vettes used them from the factory and that was back then. Could have been a performance enhancement or to prevent boiling the fuel
![shruggy shruggy](/ubbthreads/images/graemlins/custom/shruggy.gif)
Several versions are available google "Holley heat shield".
Also depending on how long your valley pan has been in place they have been known to burn through but with a blocked intake I would think that added thickness of the intake would heatsink it away. but then again it may be heatsinking the intake enough to pass it onto the fuel line
I do know on one persistent b-tch, we made a base like the one shown, extended it to cover the entire length of the carb on the R side, then bending it downward to clear the fuel line while blocking the heat. 10 years ago and he hasn't had a problem since
![beer beer](/ubbthreads/images/graemlins/custom/beer.gif)