Points of Information
FB, the US Mk 43 was a lightweight HE torpedo (HBX), the first capable of being dropped from helicopters. It had a range of c.2.25 nm. RAFM Cosford has one that, for training purposes, could release dye and be recovered. (Produced 1951 to 1959) The RN bought 50 of them.
The US Mk 45 was the nuclear torpedo (W34 warhead), in service from 1959 and as far as I know US only and submarine lauched. (Produced 1959 to 1976)
I presume the St Mawgan weapon referred to was the US Mk57/B57 for Nimrod. (Produced 1963 to 1967)
Over the years the RN made proposals for nuclear versions of both the Mk8 and Tigerfish but they didn't get far.
Never come across an air dropped nuclear torpedo but then I never knowingly had the need to know.
Mud-moving Hunters to nuclear armed torpedos PPRuNe thread drift at its best.