1965 Dodge Dart high RPM issue

I’m going to try an slap on some 180/85R13 and see if that helps any...I’m also going to spin the wheel again and count 1/4 turns and see what number i come up with... I fear that i need to find and replace the ring and pinion gears. But i want to do all avenues before i break down and do the rear-end. I have only done 1 in the past and it was on a Chevy and that was years ago. I can pay someone to do it but they want an arm and a leg. So next is to put close to original size tires on and see what happens. I’m also going to do a tranny flush for ***** and giggles.