: I have a 1990 Olds

I used an 83 Grand Marquis for a while. It was a beater as well.

Go to a nearby wrecking yard and look for big vans ( maybe commercial - as in plummers, air-conditioning/heating companies ) and pull off the top racks. You can get them for a few bucks. Bolt them through the roof, lots of silicone and big body washers to seal from rain. Once you have it bolted down, with cross bars, you can do many things to tie a boat to it.

The big vans generally have big flat attachment brackets that will work well on top of the big cars.

Rehd