Newbie with my first Cuda at 62 yrs old

What sending unit did you use? Most replacement units have a significant fudge factor. You can either get the original one rebuilt or there is a unit that corrects for what your unit reads. For me I just paid attention to how much gas I put in the tank and knew where the needle read. I just serviced my sending unit and 10 gallons gave me just a bit over 1/4 tank on my 16 gal tank.