Hi, new here, need help with a drop... Clearance

[superhondaz50]

Hi, my name is Ryan and i'm fixing up a 69 c-10. This truck belonged to my best freind. He was recently killed while riding a motorcycle, and his father gave me this truck. I want to fix it up as a tribute to him. So my question is... how low do you think I can drop this truck? It has full length headers so i'm worried about ground clearance. If I can I would like to use 2.5 spindles in the front and 4 inch coils in the rear,(also what other parts do I ned for this height of drop) if I cant I am thinking about a 1/3 drop with coils.
Thanks for your help!