Can anyone tell me, on a "book" chassis and wishbone setup are sierra uprights interchangeable with the cortina, obviously with inserts to take top balljoint. But is suspension geometry affected, what else do I need to consider if I can use them?

Not a direct swop.

what mods need to be done to the wishbones? or anything else ?

The geometry is different. Not sure by how much.

You could buy the wishbones ready made. Gts panther ones spring to mind and then just bracket the chassis accordingly.

Bare in mind the Sierra track is some thing like 7” wider than the Escort so you may want to redesign the fronts to give you a wider track any way.


regards