Hello,
My chassis is 4" wider than 'book'and I am ready to make wishbones.
I would like the track between the front and rear the same ,so is it just a matter of lengthening the wishbones 2" each side but keeping the shock mount same as book,also will I have to lengthen the escort rack or will it be easier to shorten a seirra rack.
I was going to use cortina uprights etc,but they are heavier and a bit thin on the ground compared to seirra one's,I know you can buy an insert to fit in the seirra upright to accept a ball joint but reading on here no one really knows what ball joint to use at bottom without modifing the upright i.e taper drilling it.
Also are the dimensions of seirra upright identical to cortina or will I have to totally redesign the wishbones?

Is the chassis wider in the area of the front wishbone mountings? If not, then you will need longer wishbones in order to keep front/rear track the same (Bear in minsd that they don't need to be the same)
The spring/shock bracket should remain close to the hub, to minimise the bending load on the wishbone. You may want to raise the upper mounting and use longer shocks to preserve to operating angle of the spring/shock unit.
I have been trying to solve the lower balljoint issue with Sierra hubs for some time now, no luck yet.
Have you considered using the MK wishbones? I know they do a longer set for Sierra hubs, and have a solution to the lower BJ issue.

John