The only link I can see between Hunt and the UOP Shadow is a one-off 'F1 vs CanAm' race that took place at Luguna Seca, I think in 1974? James and JP Jarier were in single seaters, Oliver and Follmer in the CanAm cars.
Edit- according to 'Racing Sports Cars' website he was on the entry list to drive a DN2 a couple of times in 1973 but didn't. It also shows him co-driving a Gulf Mirage at Kyalami in the 1973 9hr race, finishing 2nd.