[Canuck]

15 inch with 245-60-15 Puts some meat on the ground and fill the wheelhouse nicely. !5x7 were found on a lot of Cutlass, MonteCarlo etc from 75-77.

Wheel Options for Olds Cutlass from 70-72 were as follows.
14x7 steel wheels, coded XT or IF, either are interchangeable. In 1972 if you ordered the wire wheel covers you automatically got the 14x7 IF as they were about 1/8 deeper on the spider and the wire wheel cover needed this extra clearance. If you tried to use the wire wheel cover on an XT it bottomed out.
SSI, this is the magnum style wheel, 5 chrome spoke, black rim with trim ring. Chevelle Wheels are painted silver,not chrome. Both use the same chrome center cap. For a brief time in 1971 these wheels were all Chrome due to inventory shortage of the regular production wheel.
SSII, these are the Olds Rallye Wheels with the 5 oval openings used with trim ring and painted argent for 1970. You cold only get body colored wheels in 1970 on a Pace Car or Rally 350.
SSIII,Probably the most common Olds wheel, as a SSIII these were always painted body color and were available for the next 15 years in either 14x7 or 14x6 in the 80's. Two types of bezel opening trim were used. They were also available as 15x7 in 1975-75 with the bolt on cap and from 1976 and later had the snap on cap.

In summary, authenticity NO No's

Painted SSIII on a 1970 other than Pace Car and Rally 350
Chevelle painted SSI on any 70-72.
All chrome SSI on a 70 or 72.

Hope this helps.

Paul