So I came across a 4bt through word of mouth and the guy wants 1200 for it. Its a 1978 Grumman Aluminum step van. Guy says it was rebuilt from the ground up in the 90's by Frito Lay Rebuild Center in Ohio. Its about an hour away from me and Im going to go look at it. What do I look for? Where are CPL numbers? What do they mean? It has a TH400 tranny BTW.