I wouldn't go with a '79, it prolly has crappy heads and it's carbed. The carb would make the swap easier, but not as friendly as a daily or cold-weather driver.
Amen ash....take it to the 5.0 forum for "expertise". The later model efi (HO) motors are really the only ones worth swaping ...the rest are a 150hp versions i believe....then again, im not an exspert.
I would get a 88-93 5.0 HO and then convert it to carb, those years are ideal plan for you. parts will be really easy to mod with those years. good luck.