Thoughts on new carb !

I was reading on line information from Holley about carb. set up, and they had a small note that since my car is an auto trans, they say to have it in drive to preload the engine when setting the air fuel mixture and idle speed. I think I will retry the carb adjustment that way to see if I can get it to idle better while in gear. It is aways 2 steps forward and 1 step back, I yesterday needed to adjust the exhaust system, was hanging to low, had rear of car up in the air on safety stands gas tank was about 3/4 full, started to smell gas checked out gas tank was leaking from the fuel sending unit lock nut now mine you I have has the tank in and filled many times and never had it leak. I opened the fuel cap to vent think it would stop the leak because of high pressure which did help, but it did not stop it completely, so pump out the gas to below the fuel sending unit to stop the leak, now I am ordering a new gasket and ring, the gasket and ring came with the new tank I installed from Quanta gas tank 4/27/2012 !.