I have a 79 Ranger.  Its a fiberglass boat, I hate the way it is set up.  Can you cut out all of the fiber glass storage and rod locker and re build it with wood?  Or will that desroy the integity of the boat?

I dont see why not if it is done right, just make sure to refiberglass it, dont leave the wood bare for it will rot or break easier. As for integrity, I don't know if it will hurt because it is a 79.

I would suggest posting a picture of the boat and give us an idea of exactly how much you intend to cut out. 

Based on my recollection of 79 era Rangers, I'd say cutting out the glass and replacing with wood is a bad idea - unless you are a fiberglass guy and plan on encapsulating the new wood with fiberglass and adhering it to the hull structure in a secure manner.

However, if your intention is just to use it on ponds with a small motor on it you should be OK.  And accept that the wood will eventually rot.

Also, before putting any time and effort into rearranging lockers, make sure that your transom and decking are solid.  The wood on the older boats sometimes gets soft (even when encapsulated) due to 20+ years of holes being drilled and not properly sealed.

Given the amount of work and cost of doing it right, and the market for old rangers, I'd consider selling it and buying a hull design that works for you, before tearing it up.