I think it would be easier to buy another whole K5, non running or whatever, and swap all your parts into it. If you decide to make it perfect. It may be less cumbersome than a body swap and you can gain a lot of extra stuff and stuff to sell.
But, being a wheeler, may be best to do as suggested and just straighten the glass hole and get a new glass installed. Then continue to drive/beat/wheel the truck as desired. Leave the mangled metal as is.
One thing you NEED to consider is a roll cage. Now that the roof has caved in once it will cave in easier the next time. You don't need that on your head.