In John Mahoney's book,Full Tilt,there are two photos from 1971 with welded in cages. The 29 car, says Stapp on the hood but that was Boston Louie Seymour's number, with Joe Saldana at the Hulman Classic on May 1 and Paul Leffler's car with Sammy Sessions in the same photo. There is also another photo of the Leffler car at New Bremen in April. That's the earliest photos I could find of USAC cars with welded in cages.

Vern Plotts