[brian_]

It will electrically work upside down, and with no active cooling being upside down shouldn't matter to cooling, either. I would want to look at where all vents are located.

The battery case is not intended as a load floor - I wouldn't use it that way. I would consider mounting it right side up, and positioning crossmembers to support a load deck above it to miss the humps in the pack. The deck is going to end up really high, if the bottom of the battery pack sits in the original truck box floor or at the height of that floor - the deck will go right over the wheel wells which normally protrude into the truck box.

 

[brian_]

on my 1/2 ton the space between the wheel wells is 4 feet I think the back will just fit in between the wheel wells as it measures 47" wide...

By going over the wheel wells, I meant that with the pack sitting on the box floor (down between the wheel wells), the top of the pack - and thus the top of the deck you would build over it - would be higher than the wheel wells. It looks like that's what you're planning.

Of course, if the pack doesn't fit between the wheel wells (which is likely for a compact truck) the whole thing gets very tall.

... and if I flip it upside down and flip it front to back the big hump will drop right behind the cab and sit much lower in the bed...

It will only sit lower if you cut away the floor of the box where that hump (which goes under the rear seat in the Leaf) needs clearance.