Have two v belt setups I am about to remove the air pump and all tubing on, couple questions ?

Best exhaust manifold plugs are 5/16 flared ?

After cutting air tube off flush at GUTTED cat, anything special needed to weld hole shut on cat ?

I even want to remove pulley that was driving the air pump, has anyone tried to separate the v belt pulleys ? I realize I would have to use a spacer instead of the pulley to locate fan properly ?

Thanks,

Bill E.