Fix the engine leaks. (sure doesn't look leaky!)
Install O/D trans.
Install aftermarket a/c.
Tail light bezels.
That should pretty much leave you broke again, but with more fun on your hands driving to the po house.
Any $ left over - low budget disk brake upgrade. Might even put this above the trans upgrade... (unless you've already done that.. 5 lugs I see(?))
Nice looking truck btw. If you've already done the disks, maybe some interior resto, if you need it.
And maybe your last $5 on rattle can semi-gloss black to detail your grille letters and headlight buckets
EDIT: Ok, sorry, keep getting more ideas for YOUR $5K. And I'd throw on a factory C10 air cleaner or a dual snorkel (black).