you should do more research than wiki. Saying it is derivative of Long Ranger is like saying the Ford Explorer is derivative of the F150.
Wiki is a quick & concise source, at times, for info.
The original Bel 206A (Jet Ranger) had an Allison 250C-18 engine with about 250 hp, IIRC. The transmission was rated at about 317 hp (actually, the torque associated with that HP and RPM.
Bell did incremental upgrades over the years, going to the C-20B engine for a long time. The licensed Agusta in Italy to manufacture them. I put about 600 hours on an Agusta-Bell 206A, which had been upgraded with the C-20B engine, flying around East Africa. My two main home fields were at 5,500 ft and 6,620 ft elevation. I flew full loads into landing sites at 10,500 ft elevation... then waited around until almost dark so that it cooled off enough to manage a sliding take-off.
Bell customers wanted more room, so Bell stretched the 206 to add 2 rear facing seats. This had the JetRanger III engine/transmission and was designated the 206L LongRanger. Upgrades in engine & transmission eventually led to the 207 with its 4 blade rotorhead.
I first flew the JetRanger in the TH-57A Sea Ranger version as a USMC 1st Lt at flight school in Pensacola, FL in 1973.
If you are not happy with wikipedia, try this:
http://www.aviastar.org/helicopters_eng/bell_206_longranger.php