In the Aftermarket/Performance Line:
TKO500 - 5spd, up to 500ftlbs torque
TKO600 - 5spd, up to 600ftlbs torque
T56 Magnum - 6 spd, up to 700ftlbs torque
All three have the rear, mid and front shifter location, with the front most position requiring an optional kit to utilize that position. OEM Tremec's are designed specifically to the OEM specs, and have a fixed shifter location, lower design torque ratings, and other internal component modifications specified by the OEM to pare back unit costs. Each of the Aftermarket/Performance tranny's offers two different ratio spreads, depending on your application. The T56 is about $800 more than the TKO600, so the total cost for a package like I bought should be in the $3900 to $4000 range. It's the old adage, "You get what you pay for".