Body Work - Behind the rear tire

[Seabiscuit]

Yesterday the rear passenger blew up while I was on the freeway. After replacing the tire, lug nut and bolt, muffler I had the truck cleaned and buffered. There is still a giant gash behind my tire. See the picture below. Does anybody have any tips on how to go about fixing this one?

Passenger side:

Driver side:

 

[gwaii]

that's not too bad to do.this is one of those times having a fiberglass box is a good thing.
although it's not absolutely necessary,i'd remove the fender-those ones just bolt onto the box.then i'd grind an area about 6-8" around the damage clean.taper the edges with the grinder down to the outside over a 2-3" width.now you can use masking tape on the outside to form the shape of the missing section.don't skimp,you'll want at least 5-8 layers.now turn it over again and use fiberglass matt and resin to rebuild the area from the inside.build the glass up to the original thickness and overlap to the edge of where you originally ground the surface clean.

once this has set,remove the tape,and grind the outside surface to shape,use a bit of filler to get it smooth,and prime and paint as with any other repair.
and fix that crack on the wheelwell while you're at it.

 

[Seabiscuit]

gwaii - thanks for all the usefull information. what do you recommend for the crack on the wheel well?