if you're not particular about it, just tape down the accel and dead pedal with very strong 3M tape, over the original pedal/plastic. The accel and dead come with screws, and you'll have to drill into to your plastic backing and the original accel pedal to screw it in. so if you intend to sell them later, just tape down.
but pls take note that it's potentially very dangerous if it ever comes loose and jams your brake pedal travel. so buy proper 3M tape, dont use blutack ok. I still have some 3M tape leftover from my install. you want?
brake pedal, just peel out your original brake pedal sleeve, and drill or tape in also. better to drill. next time you uninstall, replace the brake pedal rubber, and all the holes underneath will be covered. no issue.