If you want to keep the price down then I would buy the metal cut it and tack it together. If you haven't welded before then it may be best to get someone else to do the welding. With something that will take the stress of a diff bracket, you don't want to take any chances. Have a look for somewhere like 'Metal Supermarkets' for the metal. They specialise in small quantities of metal, but it does get expensive if you want them to cut every piece to the correct size. probably cheaper to buy an offcut and get the hacksaw out. MIG's are worth having and they seem fairly cheap now. Cebora are a good make, I've owned one for 20 years.....The only thing to be aware of is that as you weld brackets like this they do tend to distort as they are welded so if you were making lots you would make up a jig.