I had to do a fair bit of work to the doors to get the 5-3/8's in there. I had to cut some steel out and weld some back in, move the window track a bit, and make a spacer for them, and there is no room in the cabin to build a pod that sticks out. The 6.5's are a lot bigger so I don't think it is possible to fit them in the same spot.
This vehicle is a bit unusual in some respects. It is a big vehicle, but the cabin layout is not spacious due to a very large trans tunnel. There is not even room to fit a crossover in either of the kick panels!