My 520 is running 27x9r12 in the front and 27x11r12 on 5+2 wheels. Measures about 52-53 wide in the front. The wheel wells on my silverado are 50 apart l. When loading it tries to drive over the wells then slips down between when the weight gets heavy enough. Loads easily. I can a piece of plywood that fits around the wheel wells and covers the tailgate when its down. I have a 6'6" box. I have a 6 inch lift and 35s. The ramps i have are curved and hinge in the middle, longer than normal straight ones. Not sure what brand they are but the extra length and slight curve is really nice with that much pick up height.