your best bet is to take an afternoon and pull off your bumper and measure everything. There are only 4 bolts that hold your bumper on. I built a completely new bumper in approximately 4 hours for my ranger, granted I had access to cutting and welding equipment. If you do build this dont use the goofy mounts that the stock bumper uses, personally I just had 1/4 in. brackets laying around that I used. They had a 90 deg bend in them and a slotted hole on each side, after I had cut and welded my bumper I just bolted it onto the brackets which were bolted to where the stock bumper was. As for my actual bumper I had some 12 gauge C channel laying around so all I did was cut small angles out of the top and bottom, bend, then weld. I basically eyed up the first side to match the curve of the truck and then from there took measurements so the other side would match. Its not the most technical approach but from my experience with inventor, it would be quicker and easier to just go build it. Then worry about drawing it. Dont get me wrong I absolutely love inventor its great for drawing out pieces that you need to get fabbed, but for something like a bumper its not very helpful unless you need the drawings.
After all that I'm curious, have you gone through and looked at pictures to find sorta what you want?