For the sending unit, your best bet is to have it rebuilt. Nobody makes an aftermarket replacement for the full size models unfortunately... only Firebird, GTO, GP, LeMans, and Tempest I believe. I sent mine to TriStarr in upstate New York. "Fuel sending unit specialists" they call themselves... see
http://tristarrradiator.com/
I read those recommendations for years (with a non-working gas gauge in my 69 Executive) before finally sending mine in a couple months ago for rebuild. It was in the neighborhood of $240 I believe, a little pricey but so nice to have it working again! No better time to have it done then when the tank is off, but they run about 3 weeks behind so Id plan around that and/or check with them first.