When you download the factory Chrysler service manual from
www.mymopar.com, it has a section which details the speedometer gear combination for particular tire sizes. Take the original "inch" width and convert to metric, then add a "75" to it for the complete modern tire size equivalent. Which would make the orig 8.25x14 size into P215/75R-14 equivalent size.
The orig power disc brake size would have been 8.45-15, which woiuld be P215/75R-15, which would have been a slightly taller tire. Which might explain the "65" aspect ratio, which would result in a shorter tire, possibly more the diameter of the P215/75R-14 tires it probably had from the factory, with drum brakes.
There are a few tire size comparison utilities on the Internet. The first one I found was at the Mazda Miata Club website. Put in the metric numbers for one tire, then the tire size it's being compared to. It has a graphic of both sizes "stacked" onto the other and the related speedometer calibration differences in "revolutions/mile". Using the "revs/mile" number, you can then used the tire specs for the tire being considered at
www.tirerack.com to determine what sizes might fit your reve/mile criteria. Have to do it with the particular brand/model of tire from their "Specs" chart for each one.
Personally, I've had very good luck with BFG Radial T/As, in both performance and extended-use durability. The P225/70R-15 size in raised white letters is one of the "go to" tires for '70s muscle cars. That size is also equivalent to the G70-15 size in physical dimensions. Unfortunately, they have become a bit more pricey in more recent times.
Congrats on your purchase and enjoy!
CBODY67