Cherokee shoulder seat belt replacement

My warrior is fitted with shoulder strap seat belts anchored to the
upper side of the plane, just above the second window. From the looks
of them they were original equipment. Now - I need to remove the
retracting mechanism so I can have new belts attached. After removal
of the plastic cover plate I see the spool, bolted to a bracket which
is attached to the fuselage with three phillips head screws. The bolt
just rotates so I assume it has an unsecured head that I can't get to
so the three screws are the only way to remove the retracting
mechanism. The only problem is that the screws are so close to the
spool that I can't get a proper bite with a screwdriver. A closefit
screwdriver will simply "cam out", I can't get any lateral pressure on
it. I might be able to grab the screw head with a pair of vise grips
but hoped that someone on this group would have a smarter way. If you
did - where did you take the equipment for fixin? Leo