I did a job like that several years ago. It was pretty simple. The house was a '60's custom w/ shakes. The contractor had put 1x6's & used a 1x4 for spacing them. With shrinkage over the years, new 1x4's fit nicely with only an occaisonal rip needed. Renailed & replaced (where needed) existing. It was way cheaper & less time as well. Unconsequential gaps.Than God for nail guns.