I would use the new laeger style ball joints. JD, JB, Alba, Houser, and others also use them. They are inexpensive, strong, and all sealed up. The open style ball joints and heims are a pain to keep clean and lubed. The most important thing when making arms will be the castor. If you put heims on the upper a-arm pivots, then you can adjust the castor. If you just put bushings on the upper pivots, then you will have to have the castor pre-set in your jigs. Castor will greatly affect the handling and it needs to be right.