anyone know where to order a decent Nv3550 5sp for an xj 2000 an are there any upgrades that can be do to make it tow 500 to 600lbs better plus the weight of the passengers plus jeep i don't care to do 70 on the freeway just want less stress ???. I don't want a bigger motor but if I do what changes would need to be done for a 4.3 v6 ???