Here's my old '70 Tempest T-37 with 245/60s and 275/60s on 15X7 Rally IIs.
The 275/60s are a little wide for the 7" wheel, 7.5" is the minimum recommended rim width for that tire size (most manufacturers say 8", at least one says 7.5").
Looked and drove just fine, no instability while cornering, no issues.
