Blacktop rods are a little shorter/longer than silvertop as blacktop Pistons and rods fitted to a silvertop stick out the block a few mm so you would need silvertop rods to run the RS Pistons in the silvertop. 1.8 head and 2l head are the same head aslong as they're both silver or blacktop so wouldn't worry about the head just cams and valve springs, Injectors for 300hp I would be inclined towards RS injectors, astra vxr injectors or the rover turbo do some high cc injectors, I have red bands which are meant to be 380cc at 3 bar