I am having trouble setting the time/fuel mixture/ect.

My vehicle sat for a number of years and I am now in the process of getting it running again. I had it running decently for a few months but now I cant get it to start or run right. It starts up great between 35 and 45 degrees advance timing but once running tries to die out on me and immediately dies if I put it in gear. It will run fine between 5 and 20 degrees advance timing but if I try to start it at that timing I feel it popping in the exhaust and doesn't want to start up. Sometimes it will stay running in gear at that setting but its hit and miss and always tries to die even if it stays running. I have an extreme case of lack of power in the rare event that I can get it to move itself. I have so far attempted to set the timing followed by replacing the distributor, checking the timing chain (and replacing the timing cover gasket), replaced Cap and Rotor as well as plugs and wires. Found white residue on 2 plugs so changes head gaskets, and intake manifold gaskets. There is also a very strong smell of fuel but I cannot seem to reduce that no matter how much I attempt to adjust my fuel. The problem persists after all of this and I am at a loss as to what else it could be. The engine is Carbureted using a Holley Street Avenger 4 Barrel carb and all of my vacuum lines seem to be in good shape and have suction. I appreciate any help you can give me!