dont know what year your truck is, but my 38's cab is very small. If I decide to switch to buckets, I am going to find them out of a 4 door compact. the seats themselves are thinner in the rear which will allow me to move the seat back further. I will have them reupolstered, but I think finding a small frame to begin with will definitly result in a smaller finished product, regardless of how much padding is placed on top of the framework.
