Give me pointers on buying a square body

[3672300]

So Ive narrowed it down to 3 trucks, struggling between the 3 and looking for advice on which is the better one to buy and enjoy as a weekend driver/toy.

1) 1979 K10- $4000, black truck now painted brown, ex-shop class project truck, minimal rust in cab corners, small lift and tires, 350 crate motor, auto, basic clean truck.

2) 1975 GMC High Sierra- $5900 still looks factory, paint faded, minimal rust, 400 small block and 4 speed, needs interior upholstery, needs tires, most original of the 3 im looking at.

3) 1978 K10- $3400- Original yellow truck now blue, 383 crate motor, auto, rust on all 4 corners, looks the nicest from 50 feet, definitely needs new interior.

I guess im just torn as to if its better to buy more of a project, or buy one more complete. Did you spend more on the front end of back end?