Need major help with rims

[SnS C10]

hey everyone! i picked up a set of 15x8 centerline drag stars for the front and 15X10 for the rear. the front has 245/40 tires and the rear has 305/50 but anyways the rims are the 4 3/4" bolt pattern. now i can run adapters but i would rather not. So here are my questions:

Can the mounting holes on the rims be slotted out 1/4"?

Are there any rotors with the 4 3/4" bolt pattern that is a direct bolt on for our trucks like from a chevy blazer or similar?

What can be done with the rear axles to get the desired bolt pattern?

thanks for looking!