I don't know about the angler, but the cruiser of that vintage had a raised fiberglass floor over the cockpit. A year or so older had a two part floor which could be removed. Prior to 2005/6 the boats "floor" was generally the inner hull.
A built up floor would would not be a detriment. I would not want a floor screwed to the inner aspect of the hull. It could be laid in a sealant or adhesive and be fine.