Gene has given you wise advice and wisdom. Heed it. Many projects have been started and then abandoned when they become overwhelming.

I think that the full sized truck frame will be too long and too wide, a tape measure is going to be your best friend (even if you don't like the results).

Unfortunately there is very few quick or easy frame replacements, It has been said that the best frame (modified) for a project is the original one. I believe that to be true.