Normally, provided you check the fuel bowl in the carb doesn't have rust holes that will drain it, you can get by with just the tank gasket and diaphragm on the side of the carby.
All I would do is clean it thoroughly and throw a new gasket (GA spares GSL695) and diaphragm (CAM496) into it.
See how it goes, then you may need a couple of bits like a new main jet/needle (briggs 299060).
And maybe a new pick up tube if the wire is all corroded (if itβs a 2-3l tank its briggs 391813)
