Rust Issues, need some opinions!

Well, my '74 D100 has some pretty rusty floorpans that have some pretty bad holes. I also have some rust hanging around between the drip rail and the windshield in the front of the truck and it looks pretty gnarly. i have two options really that I can think of.

A. weld in some new floor pans and try and fix the rust under the drip rail

or

B. get a whole rust free cab from the junkyard and solve both problems at once, but have to wait til I can get the truck painted or have time to prep it