It's almost trivial to repair cracked pants, if you put a little effort into it.

Here goes:

- Remove the wheel pants
- Tape the outer part of the pants together tightly with masking tape.

+ You can save some sanding later if you have minor cracks, if you put wax paper over the outer crack, to shape any epoxy that may seep through.

- Cut several strips of fiberglass cloth, that you can lay on the inside of the cracked wheel pant. You want to minimize the number used at one time.

- Mix up some 30 minute epoxy, and add about 30% Isoprophyl Alchohol to it to thin the mix. Some people use Acetone, but this may ruin paint.
- Apply the thinned mixture with a brush to the inside.

- With a gloved hand, lay the fiberglass strips to the inside of the pants.

- Apply more thinned mixture until the fiberglass seems to all but disappear.

- It is OK if the fiberglass extends beyond the wheel opening, as you can cut or sand off the excess easily later.

- Let dry overnight, preferably inverted.

- Repeat if desired but I find two fiberglass strips are often more than enough...

- Remove the tape and wax paper.

- Now for the outside you have your choice, you can apply epoxy and filler, or use something like Bondo.

- Apply the Bondo, let dry, and sand the pants with progressive grits of sandpaper until somewhat smooth.

- Clean, prime & paint.

Done.

BTW: The same works for cowls too. I have repaired HUGE holes in cowls or remodified the cowls for completely different engines and mufflers this way.