My 4-speed Hemicuda had 4:10's and F60 Polyglas GT's. It redlined at 125 or so. Redline is 6500 so 3250 would has been 62 mph. Mine was 4 speed though so no slippage. Your RPM's sounds like 4:10's. If the Dana doesn't have a tag, just jack the car up and turn the back tires one revolution by hand. If the driveshaft turned 3-1/2 times it's a 3:54, if it turned 4 times it's a Dana.