This has gone unanswered for too long. I haven't found anything as for yet but the Hot Wheels/JWR AMX was a modified version of the standard machine with a 390ci American Motors V8 bored to 401ci (6.4 litres) running on petrol in the NDRC and BDR&HRA Street divisions.
In 1971, the Hot Wheels AMX was featured in 17,000,000 boy's comic's in a promotional competition with the American owned Mattel Toy Corporation. Prizes ranged from complete Hot Wheels racing strip sets to replica's of Ed Shavers AMX which, at the time, didn't feature in any of the HW catalogue range.