If it's a 72, I'm almost sure it's got a Quadrajet, right? They're nototious for the float getting soaked with fuel (it's plastic), and sinking. The Q-jet is no picnic to work on, and even a simple float replacement is a hassle. There's a real danger of bending the primary metering rods when you try to reinstall the top.
A rebuild by a professional carb tech should run somewhere in the $100.00 range for a correct job. There are 22 consecutive adjustments during a rebuild, so unless you've got a lot of experience, "don't try this at home" applies. You might investigate the purchsae of a rebuilt carb, but be sure it's a direct swap. There are approximately 250 different Q-jet part numbers, and they've been installed on everything from a 230 cubic inch Pontiac OHC 6 to a 500 CI Cadillac.
Jerry
