David,
You are faced with the age old problem of making the hole for the screw "smaller". Have you considered JB Weld? I've had reasonable success by using a "dab" of JB Weld on the hole (to make it smaller by conforming to the size of the screw), a "dab" of lithium grease on the screw (for "ease" of getting the screw in and out) and an overnight "curing" time.
It worked on my door sills plates on my 66 Hardtop.
Jim