We have a couple of adjustable spreaders (the stock original was a straight nonadjustable). I think they'll work for you. You will need diamond wires if you get these spreaders from us

I believe your '84 will likely be solid 'glass. The glass boats were somewhat flexy from the get-go. What you want to look for is to make sure that:
--the longitudinal stringers (half-circle bits along the inside of the hulls) are still attached to the skin
--the bulkheads (inside the hulls, under the beams) are still attached to the skin. Reach in and push on the bulkheads - they shouldn't move.
--the outer decking shouldn't have any splits longitudinally, the boats were built in two halves and glued together. The glue line/flange acts as a stringer as well.
--although flexy, the hulls should not be mushy. Oilcanning (flexy) is ok, mushiness is trailer crush.

All of these are easy enough to fix, if you're willing to mess with it and the price is right. Just make sure the price is RIGHT.