All numbers match but have question

[Moms74C10]

I have a '74 Chevy C10 short bed step side. It is all original, all the numbers match. We plan on restoring it and plan to have the engine professionally rebuilt, convert it from three on the tree to floor shift, and to paint it from the original green to something a little more stand out. I was told that painting it something thats not the original off the factory color pretty much makes the whole benefit of the matching numbers null. Does anyone here have any opinions or thoughts on this? Thanks in advance for your help.