49bourbon,
I used the original LCF cab, a conventional cab and a panel truck. The roof and b pillar is off the panel truck. I flipped backwards the door jamb I cut off the original lcf cab and used it as the back of my b pillar. The inside of the b pillar is what was there from the panel so it is completely boxed in. I also boxed the bottom of the b pillar that is below the floor in between the steps. Under the cab, I continued the c channel bracing that lcf cabs have all the way to the rear mount. I also added a cab support that will mount to the frame in where the two pieces of c channel mate together in the middle of the cab. Not sure I need it because I just have the rear and front mounts bolted to the dolly I made and there is no flex at all in the cab. I even jumped up and down inside the cab and could not get it to flex. I tend to over engineer things. I would be mad if the cab started sagging at some point. let me know if you have any more questions. On a scale of hardness from 1 to 10 I would give this a 12.
Shane
