What fuel pump were u using in your 40? We're u running a evap cannister? I would go for at least a 24" stretch on a 45 cab if I was building one. But I like to be able to lay my seat back and take naps at times and have the ability to throw stuff behind my seat. What about building it into a troopy and just using the back as a pickup? My favorite stretched 45 is a yellow one that was on here. Here is a pic of it and a pick of a troopy build.1966 Toyota FJ45 Land Cruiser Troopy - One Trick Troopy