Mine is simple, functional and looks great - I have a few OLD photo's from before the interior was complete with only the temporary seat cover on - couple of years ago (and how much progress have we made since???).
All it is, is welded 2" angle iron that forms a box under the seat and down to two pieces of flat iron on the bottom. My seat rails bolt to the top surface. The flat iron bolts to the floor.
So, now I sit high enough and my legs aren't squished, and my arm sits just right on the window opening whan it's down.
I've made some masonite panels for the front and sides (2 on the front) I hold on with velcrow that I'll eventually cover with fabric or carpet, and I keep my tool bag, jack, etc. for the truck under there.
Simple but it works.
PS I got the longest seat belts available and bolted them to the floor as well.
Mine is welded up from 1 inch square tubing. I cut and laid the tubing out to match the stock bolt holes in the cab floor and tacked up, then turned the seats (out of a Mazda truck) upside down, cut tubing and bolted to their stock holes, tacked, then just sat on top of the frame bolted to the floor and cut tubing to set the height I liked and welded it all up. Has worked very well.
sooo,,, i have a confession to make... i actually have already made one, just wanted to compare to a few of the experts. Ive been looking for something to compare to see if what i have made has ever been done. I took old metal tubing from a chain link fence I removed and welded up a tubular frame. Next I took oak and finished the long sides and top. In the ends I made an oak face frame and then solid oak drawers on ball bearing slides. Its not totally done yet, but so far ive been working on it for around a month here n there... i would have to say if i did it again, even though i like the tube look, it was really hard to line it all up! thanks again for the replys n pics!