I used to work at Marshalls on the C-130's in the early 80's; now I don't specifically remember seeing anything installed on the aircraft, but I assume that the RAF birds had a simple fatigue meter that would record vertical loads - I know we had them in the little Bulldog trainers, and we had to record what the meter showed and report it back to the a central maintenance information unit, who would then use the data to calculate the airframe life.
It might be worth your while to speak with someone at Marshall Aerospace, as they have built up a substantial amount of data on RAF C-130's over the years - can't guarantee that they would be forthcoming with info or that it would be free of charge, but it could be worth a phone call. Sorry but I don't have any names to point you towards, I've been gone from there a long time.