Attached is a chart (powerdog.com) that compares different sizes mentioned above.
In a reference book, it said 1963 & 64 Rivieras came with 7.10 x 15 and 1965, 66, 67 came with 8.45 x 15
consulting another chart .. found one that said 7.10 x 15 converted to a 225/75r15 and a different chart did not show
the 7.10 size but had 8.45 X 15 converted to 225/75 r 15 so there may have been a tire industry change in designations.
Gene above said he liked the 205 because of the shorter sidewall, note the 225/70 sidewall is only 1/10 inch taller and the 235 is 1/10 shorter.
When you use powerdog, the first tire you enter should be your base as all the other are compared to the first entry.
Specification
Sidewall
Radius
Diameter
Circumference
Revolutions
Speedometer
Odometer
Difference
225/75-15
6.6"
14.1"
28.3"
88.9"
713/mi
60MPH
10000mi
N/A
205/75-15
6.1"
13.6"
27.1"
85.2"
744/mi
63MPH
10436mi
-4.2%
225/70-15
6.2"
13.7"
27.4"
86.1"
736/mi
62MPH
10323mi
-3.1%
235/65-15
6.0"
13.5"
27.0"
84.9"
746/mi
63MPH
10466mi
-4.5%
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