Knowing that a 270 coil is for a ZL2 hood, and a 298 coil is for a Z28 with a flat hood, is there a difference between the coils other than the angle of the bracket? Is the angle the same between a 293 coil bracket and a 298 coil bracket? Is the coil itself the same between a 293 and a 298?

I'm not sure about the brackets. The 270 coil is shorter so that it doesn't interfere with the ZL2 breather.

Coils are physically the same.

For sb ZL2 applications the '67 275/327 coil bracket was used to clear the air cleaner.