you should be ok depending on the truck.. I'm 6'8" 255 lbs and drive a long hood Pete which aren't the most roomy trucks on the road, I have a few inches to spare when laying down in the bunk..Standing up I do have to duck down though.. FYI, on some trucks the drivers seat cushion can be unbolted from the seat frame and moved back in the frame for more leg room...
You would fit perfect in a Western Star! Problem is that not many companies have them as company trucks. Kind of the Cadillac of big trucks. Another really big truck with lots of room is the International 9900. Check out the individual truck manufacturer's websites. They will have all the dimensions of the trucks and most of them have inside photos and videos. Some have some pretty cool 360' shots. The one on the Lonestar truck is pretty cool too!
Besides the studio W9 this is the best truck I ever owned! Never, ever had a problem with this truck! Though cabinet space is limited, living space is quite large. We actually ended up setting up our cabinets using those rubber maid type cabinets found at Walmart. Worked really well!