RDSAluminum Perry FL. is who I bought my two tanks from. They make the tanks to order. Replaced both main and Aux on
my 93 23 Gulfstream. Both were about 95 gallons each. Had the special coating put on the tanks to help prevent corrosion.
While not for a Grady, I had Sunshine Marine tanks in Florida build a 120 gallon tank for my mako. They were less money than the local options, including shipping. Coal tar epoxy coated, built to my drawings and measurements. Fit like a glove. It was about $10 per gallon. This was in 2015, if I recall correctly.