I don't weld but I've seen, heard and participated in the process and as far as I know you have to heat up the cast iron to weld to it. I held the torch on a truck axle to weld a bracket back on. A shop would be your best bet.
Glen, what did you say? I like those round ones alot better too. I think my friend did something similar only going thru a shop at a truck stop. So Napa is just as good and probably alot closer and easier to use. Hopefully your shop teacher will let you use the press, my teachers were cool with stuff I did cause I helped them out alot doing things after school. I knew and still know all 3 of my shop teachers(machining/welding, smallengine/auto, heavy equip/semi) very well. In my opinion they are the best teachers there with science coming in a close second. I can't wait to see your results, a yellow fender like that will be very cool!