I would look at a 4.0 before a 5.0. Easier to do, similar results.
Using well picked stock parts probably about the same jump as 2.9 to 4.0, maybe a little more.
If you get hp greedy and start grabbing Mustang stuff you get a slightly better bottom end (to a 4.0) with a drastically better top end.
With a standard roller cam and E6 heads they are brutal at low RPM. My biggest regret is upgrading from them to an HO cam and E7 heads.
The 4.0's big perk (and IMO about the only one) is it will drop in where a 2.8/2.9 once lived. 2.8/2.9's used rather flakey transmissions so that can be offset partially offset that way though...
302 will require cooling system work, transmission/transfercase and driveshaft work. It is more $$ and time, for me when it rears back and is belting out its battle cry it is all worth it though.
For a dd that I didn't really care much about I would find the first low mile V6 and move on. A healthy 2.9 isn't really hurting for power for just moving the truck around.