Doesn't need to be adult size, and doesn't really need to be a baseball bat. That's just a handy way to have a roller that's easy to place between the tire and the fender. A round piece of pipe would do the trick. Adjust the pressure/space between tire and fender with your jack little by little until you get the clearance you need.

Some have recommended using an electric heat gun to warm the metal and paint some, with the idea that it would lessen the chance of paint cracking.

 

FWIW before you do any fender rolling,
I would suggest you try some pulling first.

Put on a pair of heavy leather gloves,
then grasp the lower edge of the fender firmly with both hands,
then gently pull outwards evenly.

NOTE you will be grabbing the portion of the fender where the tire will fit,
find a center line for the tire then put a hand to either side of it.

NOTE this is best done after the sun has warmed up the metal.
you will find that the fender will indeed move outwards,
dont pull too hard in one area as you can bend the metal.

 

Took all the advice. Reduced the 285's on the rear to 265's, pulled the fenders,removed the spacers, shortened the studs and I think the end result is great. Thanks to all.

 

Looks great! Those wheels really help update the cosmetics on an otherwise timeless car design. Enjoy!

 

+1 looking good !