ORIGINAL: w8ye
If the carb is not more than 1/4" away from the firewall, I put a hole in the firewall.
If the firewall is fairly thick...you could just dish out about were the carb center (throat) is close. This give more strength and also if you can do it keep the behind the firewall more air tight. You may need to run a line to a dead air space from pump cover.
Capt,n