hey guys I dont really understand the offset and backspace thing, I tried but its just done my head in I am looking at buying a set of 20's for my fg mk2 turbo ute, it has been slightly lowered and I was just wondering if you guys think they would fit and how far away from the guards they would be they are front - 20 x 8.5 +40 rear - 20 x 10 +40 cant figure out how to put a picture up so here is the website for the rims is http://marsperformance.com.au/MARS-WR-5x1143-20-inch-Stag-Concave-Style-Matt-Black-Alloy-Wheels-Rims-Ford-FPV-Falcon-FG-Territory would be great help, cheers in advance