I am also wondering if one of the emissions controls is askew. When I got the van it had an LT 1 full race engine. It was miserable. The van is a grocery getter and shop van and general enjoy the drive machine. Changing the distributor solved the no spark on occasion issue, at least for now. It does go through approximately 1/2qt of oil every 3 thousand miles. Oil colour is light tan at 3 thousand.
I might check the carb mounting bolts, manifold bolts for leakage. I will recheck the hoses. When we first got the van, all the emissions were unbolted and gone. I had to replace everything. We have no emissions test in this state but I still feel it is the right thing to do. An awful lot of the devices I had to get from a boneyard. The engine is not really broken in yet. At 500 miles we left Los Angeles and came back to Floriduh. We drove tender and the engine did not consume more than 1/2 qt. of oil. That cam has amazing low end power and we never have had it over 2500 rpm. We also rebuilt the rear and went from 3.23 to 2.73. I figuired with gas prices what it is going to be we could benefit from being tall.