Different firing orders?

[nibs]

Alright, Im doing this for my dad because he has really slow internet, but its kinda hard for me to explain because Im overseas and he is in Colorado. HAHA Anyways, my dad bought a 350 for his truck from a guy that claimed that the engine was from a race-based car. Well, today he went to start it up and it wont go. He has spark, he has fuel, and he has compression. Everything is good to go. After he talked to a buddy of his, he learned that you can change up the timing and be able to change the firing order for high performance. Now, my question to you is, how many possible firing orders can there be? I can only imagine there are only one or two that could actually work, and keep a smooth running engine. Any firing orders that I can give him to try? I really appreciate your help!