there is a standard cab that holds three people side to side. then there is a crew cab that can hold several more.
trucks with extended cabs
No. The F600 and F150 are entirely different classes of vehicles, altogether. While some components are shared, the cabs are not common between the two.
Some automobile companies have options to install cabs on trucks when you buy them. I know for a fact Chevy and Ford does this. If you already have a truck you could go to a local dealer (possibly same place you bought your automobile) and get one installed. The Company LEER specifically makes cabs/caps for trucks. You can go their website and see if they have any nice cabs: http://www.leer.com/>
You should always have the same size trucks
Yes there are different sized penske trucks that can be rented. It depends on what size would best suit you and they increase in prise as the trucks get bigger.
The cabs of big sleeper trucks can vary in size depending on your desire. You can have an area as small as 30" or as big as 300". Most sleeper truck cabs have enough room for a small bed, a refrigerator, microwave, tv, and some storage. You can see an example picture of a typical sleeper cab here: http://www.pfblog.com/nakedpicks/images/Peterbilt-Unibilt-Sleeper.jpg.
"There are several car companies that offer trucks with crew cabs. Ford, Chevrolet, Dodge and GM are just to name a few companies. There is also Toyota and Nissan."
One the 1999 and newer trucks, some 2WD ext cabs and 4WD ext cabs with the 5.3 came with 3.73 gears. Others came with 3.42 gears
Cars, trucks, motorcycles, buses, trains, cabs, subways
no they are 1 inch increments of being the same
Dodge currently has 3 trucks in production for their 2014 lineup. The lineup consists of the DS Ram 1500, the D2/Dj Ram Heavy Duty, and the DD/DP Chassis Cabs.