Hi Mike,
As others above have said, its a common problem that alot of builders have come up against, my own build too.
I,m not sure if its a book error or a "foible" ( is there such a word
) of CAD, that is created from the dimensions of the original chassis design/dimensions.
I,m no CAD person but on a positive note, if a builder has this situation arise in their own build, it shows that the chassis has been cut & welded together very accurately & has been built in total accordance of the book instructions, not just on base rails but all angles throughtout the chassis.
Most builders find that a 2mm or 3mm spacer is required behind the wishbone brackets so that the spacing matches the suspension bracket jigs as per book instructions.
My own chassis required 2mm spacers .
cheers
andy