I recently added Bluetooth Sound System under the dash and enjoy riding to my favorite music. Thank you Jack for suggesting I not be so fanatical to keeping the 2+2 so original and not enjoying the car!

Great suggestion.

My issue now, is gas mileage. I get about 10 miles to the gallon around town, and heard I can have the rear end as well as the transmission changed to "HIGHWAY GEARS''

I appreciate any comments suggestions and opinions

Thanks.

Curtis

I have a 1966 automatic with a/c,so it came with a 3.08 rear from the factory. about 2200 RPMs at 70-75 mph.approx 13 mpg,I have no idea what I get in town. I guess you would have to figure out how much bang for the buck to swap gears. Also my engine was just rebuilt so my mpg may improve slightly.

My '65 has the factory 3.42 rear. I haven't measured around-town mileage, but I used to get 16mpg highway at an average 75mph, cruising at 3100rpm. I performed some performance upgrades a couple of years ago and the highway mileage decreased to 14mpg.
If you're getting 10mpg city, I don't think that is horrible for these cars. You're not going to achieve 18-20mpg no matter what gear you put out back.
Before changing gears I would analyze exactly how you use the vehicle. How often do you drive it? What's the ratio of city/highway usage? How many miles would you have to rack up to pay for the parts & labor to change? Are you willing to sacrifice the kick in the pants you get from the lower gear ratio you have now? How long will you keep the car (most buyers would prefer a lower rear gear ratio, IMO)?
As for the sound system mod, I left the original AM radio in the dash and added a modern AM/FM/CD player unit in the glove box, out of sight. I wired the stereo into one speaker in the dash and another behind the "speaker" grill in the rear seat (I know, Pontiac didn't put the rear speakers there), so my sound is front & rear instead of left & right. Once a year I swap the wires so that the vintage radio passes tech inspection for POCI points judging. Works for me.