Well here it goes....I have a 84 D100 slant 6, stockm short, automatic truck very low miles I am taking out of storage after fifteen years. The auto trans is needing attention but I want some information on using a 5 speed from an 88 d-150 I have for parts. This 88 is a 3.9 V-6 version. What are my options to make this work? I want the overdrive to get better MPG....while I cruise around in my sporty ride!