I need help understanding the mods to the car, it has a upper and lower pulley and I need a new belt but I need help with the pulley size, I measured the upper pulley from where the belt rides on with a micrometer and got 2.79 and if I measure from inside the grooves (the lowest point) I get 2.76, also on the lower pulley it measures with a tape measure from outside to outside 8 1/4in, can someone tell me what the exact pulley setup I have? also it has a 100mm idler below the upper pulley will that affect the belt length I need to order?