The 379 was a "torque-monster" producing max torque at 1600 RPM. Max HP produced at 3600 RPM (lowest RPM of any of the V-6 G.M.C. engines). Since cam profile, head design, intake design, etc. are based on low RPM and torque, installing a larger carb may hurt your performance at low RPM due to decreased air velocity, and not help the high end since the RPM is not going to be increased without changing other components.
That said, the engine should pull strong to 3500`3600 RPM.
Since you did the carb, things to check might include fuel filter, fuel pump, and fuel sock (in the tank), distributor advance, etc. Also, while difficult to set up, a leak-down test on the fuel line might prove interesting.
[Opinion- others may differ!] As to the electronic ignition, I don't like the *&^%$# things! Seems like every individual calling us with a strange carburetor problem has a "points elimination" conversion. It is the FIRST question I ask when someone starts telling me about their "carburetor" problem. The two most common carburetor problems we see these days are the PE conversion and the use of deathanol.
Remember that cell phones were not necessary until we had electronic ignitions. Now they are needed to call the tow truck! ☺
I will grant that, as long as they work, the electronic ignition will fire plugs in an oil burning engine, and will extend the life of spark plugs. I see no other benefits.
Jon.
