matching gradient direction

Generally speaking, it's usually best to cover the transition points on the vehicle either with a solid color or some kind of non-repeating texture. If you have a gradient spreading across the hood onto the fenders it's going to be really difficult to get the different print panels to match. Seams may end up visible.

The approach I would take is making one gradient for the hood and top of the vehicle where the color becomes solid at some point near the outer edges. Then I would make another gradient for the sides where the color on the upper parts of the fenders closer to the hood becomes solid and matches the color coming out from the hood. The end result can still look like one big gradient spreading out from the top center of the vehicle down the sides. You'll just have some solid area at those transition points. If colors are chosen carefully and color stops on the gradients are well placed the viewers won't notice the solid colored zone as much.

With plenty of vehicle wrap projects designers will create different graphics for the hood, top and back areas that don't even try to match up with the graphics applied across the left and right sides of the vehicle. Wrap installation is never perfect. The printed vinyl gets hit with heat guns and warped over the vehicle surfaces. Sometimes specific graphics items that need to be placed in an exact spot on a vehicle have to be printed and cut as separate items to overlay on top of the wrap.