What is the diameter of the needle and seat in your carb? How does this effective area compare with the area of your fuel line?
The old style fuel logs bolt onto the intake manifold. This makes the original style fuel log an excellent heater for your fuel...and yes we have had problems with fuel boil over with the original style log. 2x4 are worse in this regard as the fuel tends to sit longer in the fuel bowls before being used.
The bypassing regulator we have had great luck with is a Mallory 4309.
This regulator cured all fuel boil over, and vapor lock problems.
http://www.jegs.com/i/Mallory/650/4309/10002/-1