I am thinking I will be doing that on my 50 when it gets to that point. For everyday use, as long as it is apart already, I think it is a good idea to do it now to avoid stones flying up and making stars in the paint from the backside. It seems like a logical way to save a nice paint job. Plus, its a little bit of extra rust protection. Thats just my $.02

1950 Chevy 3100 5 window "in progress"
1967 Chevelle 300