If you think there's a chance that you would want to do a frame-off, do a frame-off. I had a similar situation where I started working on the truck thinking that I'd work on a small part here and there... the more I took off, the more I said "well, while I have that apart I might as well do this..." until finally I was completely down to the frame. If I had realized I was going to end up doing this anyways I would have moved a lot faster along on my project than doing it piece by piece.
