Does anyone know of Jim Raysik in Clinton, or Downtown Desoto? Here is the website: http://www.hovermotorco.com/2010/11/downtown-desoto-open-house-reveals.html
My brother used to be the sports editor there. If he was still alive, I could tell you because he knew darn near everyone in that city. I notice it has a floor shift. Typical of a 1/2 ton?
The four speed tranny was a Regular Production Option (RPO 318) available for 3100, 3700 and 3800 series trucks.
SM420 Tranny Option This just means it was sold as a real working truck when it was new..... Nothing more , nothing less .