I have a 5L with diesel radiator and electric fan. I cut around 3/4" off the top cilp to tip the radiator foreward and clear engine pulleys by about 1/2". One thing i remember is that i was to able to cut it with a sharp pair of tin sinps. As for the JTR book, I don't know but if you are using any type of flex fan make sure you have lots of clearance cause they can suck foreward at high revs. I sucked one right into rad. opps.