help with seatbelts

i have two lots of seatbelts to fit - a 3 point inertia belt on the centre front seat from exmoor trim (514/30) and some static lap belts to go in the back on the rear bench seats (two 33" folding benches).
with the centre belt there is an "L" bracket that is mounted on the floor - can i just drill through the floor and bolt on this and its spreader plate?
what is the best way of mounting the rear lap belts? i have spreader plates so can i just drill through the wheelarch?
thanks a lot. and please excuse the fact that i know bog all.

if you drill through the floor you need to get the spreader plate as close as possable to the strongest past of wheel arch but it should be an easy job to do but your need long arms