Dan Gurney practiced in a Lotus-BRM owned by Wolfgang Seidel, but after a few laps he deemed the car unraceworthy. Gurney was also entered by the works Porsche team, along with Jo Bonnier, but the team withdrew after the factory was hit by strike action.
The #4 entry was originally allocated to Lewis, then to Ashmore on Lewis' withdrawal. After Ashmore also withdrew, the slot was filled by John Campbell-Jones.
Lucien Bianchi was originally entered as #14, in a Porsche prepared by Scuderia SSS Republica di Venezia, but withdrew. He later took #19 and drove Equipe National Belge's Lotus.
Ricardo Rodriguez became the youngest driver to score championship points (20 years, 123 days), a record which stood for 38 years before Jenson Button, aged 20 years, 67 days, broke it at the 2000 Brazilian Grand Prix.
References
"The Formula One Record Book", John Thompson, 1974.