I have the 518 in my 92 D150 which I bracket race on occasion, when racing I always push the o/d off button on the dash if I don`t it goes into o/d which slows the truck quite a bit. I have a Mopar Performance/ Turbo-Action shift kit , the 1st to 2nd shift is quite hard even under normal driving but it works well. I was going to add an off the shelf convertor to try and get the truck to leave better, instead Lenny at Ultimate said he could rework my stock lockup convertor which he did and the truck responded well although it only runs low 15s my 60ft times dropped from high 2 teens- low 2 twenties to low/ mid 2.0s a little over a tenth.