Don't know if a '58 has captive bolts under the rear seats, i.e. 2 in the middle just above the tunnel and 2 more just below the rear passenger cards?
If it has, your third fixing point could be in the firewall, down in the rear luggage compartment... drill holes through and fix scab plates engine side and voila.
There out the way and behind the tar board (if you have one). Still ugly, but a good compromise...
beefykeefy wrote: