Cab_Burge
For tire size I was using 28" diameter as reported on Discount Tire's website where I purchased the tires. Checking circumference with a tape on the spare, same tire / same wheel as on the ground I get 87 5/8" which is 27.89" diameter versus the 28" reported. Negligible change in calculations as it still shows 33 teeth.

TJP & John,
For the odometer check I didn't get to it until this morning. One way trip per google maps of 24 miles. Speedometer app on phone recorded 24.05 miles. Odometer on pickup recorded 24.9 miles. This results in a 3.75% overage error for the odometer versus the 15% too fast error on the speed.

Is there anything that can be done to help or correct these old things? Clean, lubricate? Or just a lost cause and not worth it?

Larry, It has been so long (30 yrs?) since I've lubed a speedometer cable, I can't remember what is best to use. What did you use?

Thanks again for all the reply's and input.