[redmt]

The fulcrum shafts should be the same length as far as I recollect. If you refer to Buzz's picture you see the difference is to the inside of the wishbones. The fulcrum pivots that bolt to the rearend are different to accommodate the different bearing sizes.
As a side note,,, the wishbones should be reinforced with a gusset at all four points. 3/16" plate correctly fitted and CORRECTLY welded is all that is necessary. I seem to remember that 2"-3" Triangle pieces are sufficient. Make sure when welding to cross tack and weld opposing sides to prevent twisting of the wishbone to shaft.