LOL....hate to burst your bubble, but you are full of sh!t.
Just because it was a "Grabber", its did'nt get any performance above and beyond a regular Maverick.

9" inch rear??, no way....not from the factory only 8" inchers were offered.
302 motor?? yeah, but NOT with a 4 barrel carb from the factory.

Duals?? NOT!! single exhaust ONLY from the factory!! and they would not use an aftermarket "Thrush" muffler from the factory either, it would be a stock Ford muffler.
It would also have catilytic convertor under it.
Your Maverick Grabber would be equipped with a 302 2V, single exhaust with 8" inch open differential with either 2.79 or 3.00 gearing.