I had a the same type of problem with gas shooting out of the carb. New carb, new rebuilt 345, new dui distributor...everything new!! Motor would idle great, but increase throttle, the carb would shoot gas out, and kill the motor. No matter what I did the result was the same!!! I called everyone with this problem...local, Scout owners and even have a buddy call several nascar mechanics. Everyone came back with the same "try this or change that". The only thing I hadn't changed or messed with was the distributor. Heck it was a brand new $500 part!!! Crap I pulled it anyway, put the stock distributor in, and the motor came to life!!! It turned out that the new dui had a bad computer modulator that governs all the electric functions. Dui send me a new computer chip and the dui came to life. I spent about $500 dollars minimum changing and replacing parts, and more hours than I care to think about figuring this one out!! Expensive new parts are tested at the factory and can't be bad...yes they can be, and I found out the hard way!
Note: all the posts preceding this are all right on...I just had one of those problems no one could foresee.