I'm not sure about your model, but most boats of that era will have some sort of liner. Liners can be a pain in the butt, but it's not that bad, just different. In most cases, the areas you might need to get at will be covered by the liner. What most do is cut an access hole. If you're neat about this, you can use the piece removed as a lid to the access point, just make a small flange on the back side of the liner. For some things, you can fit a deck
plate, which cleans up the area nicely and provides access as required. Other areas may require a custom plate or touch of some sort.
Don't be afraid of a liner boat, the liner can hide a host of sins (and equipment) that you'd prefer not to look at. The liner can also be a place of extra storage
too, so take advantage of this hollow between hull
shell and molded interior
accommodations. Lastly, some liners are bonded to the hull
shell and serves as part of the hull's reinforcement. On other boats, the liner is just along for the ride. Again I'm not sure which is the case in your boat, but it's fairly easy to tell if you have to cut into one, usually by the weight of the liner's lay up.