A couple of years ago I was fortunate enough to find a very nice original 71 SWB out of Arizona. I'm using that truck today for a total resto-mod restoration. The truck was an original California truck that spent its life in Arizona, so it had ZERO rust. In a way I kinda wish I would have done things differently. My restoration is using a custom chassis, with LS3 engine and 4L70E transmission. The sheet metal is all original, which is cool, but I could've gotten away with using piece-meal original sheet metal parts, or aftermarket sheet metal. Since the entire chassis is custom, it would have been fine to do that way. Instead I took the original sheet metal off the original frame and sold the frame, engine, complete drive train and bed floor to a fellow board member. I'm really glad that Jim got it, because he's a great guy. But hindsight being what it is, I wish I would have kept that truck together.
That being said, you have every right to do what you want. After all it is your truck. Sometimes we have a tendency to do things that seem OK at the time, but afterwards we wonder why we did them. I'm kind of in this situation right now. Don't get me wrong, when my build is done it's going to be awesome, but sometimes I wish I wouldn't have dismantled an original truck to do it.
Point being... Just think it through before you do it. Make sure that you're fully satisfied with your decision. Once you cut it, it's a done deal. Once I sold my original SWB frame it was a done deal. Enough said. Peace out!