To use just go in to engine on any gavril t series semi and chose GS500 engine the 12 speed manual is the best to tow with but there is a 12 speed automatic but when the torque converter locks up it throws the trailer off the 5th wheel hitch at least on a extremely heavy trailer haven't tested on the lighter trailers in the game, the turbos do not have any performance gain but has different psi. This is my first mod i have ever posted but this engine is probably the best i have used i was tired of the stock engines and i didn't think any of the engines moders make are strong enough to even pull a flat bed trailer up a hill so i made my own. the GS500 produces around 11400 ft lbs of torque and around 3400 hp after 1000 rpms all bets are off that your load will be moving. i have topped out in 12th gear at 240 mph in a t75 and 270 in a striped t65 and with a 71000 pound trailer topped off at 141 mph . I HIGHLY RECOMMEND A SUPER RADIATOR , or a high performance radiator it works fine without one until you run it like it was being chased buy a baboon on fire if no one has radiators i will upload the motor with the thermals turned off until i can make a radiator for the engine. hope you all enjoy, please tell me if there are any bugs and i will work my hardest to fix then but i have been using this motor for about a month and no rings rods or gaskets of broke.