has anyone used the sierra uprights instead of the cortina ones, if so what mods to the chassis and wishbones have to be made??

I am planning on using sierra uprights, they require quite a bit of work to fit though. You'll need an adaptor for the top joint and you'll need to have the bottom taper reamed to accept the cortina/maxi ball joint. The top of the sierra upright appears to be further out than cortina ones, which would result in excessive positive camber, so you'll need to shorten the top wishbone which causes problems with spring clearance. Not exactly a walk in the park by any stretch. The upshot of this is that you get bigger, better brakes, and the ability to add launch control/traction control at a later date if you get uprights from an ABS car and have the corresponding back end.

Kingr

Bigger and better brakes? the cortina uprights don't restrict you to small brakes, i am using AP magnesium four pots on big discs, the only real limit you have is the size of your wheels, if you have small rims then you are restricted to small brakes, and you don't need sierra front uprights to have traction control etc, the only benefit i can see to using sierra uprights is that they are cheap...
in my opinion they are butt ugly and too much grief to fit to the Avon...

Gotta agree with Viper on the uprights, one of the things I like about the avon is the cortina hubs, they do look quite good. I also think a cortina calliper is just as good (if not better) than the sierra.

Point taken Viper, I was meaning as standard, which also holds for the launch control, granted if you're going to the expense of adding launch control, then adding wheel sensors probably isn't a masive problem, but it is something to consider. I agree about the ugly bit, they're not the best lookers, but hey, they're mostly hidden inside your wheels anyway, and they're about a hundred times easier to get hold of.

Kingr

thanks your helped me make my mind up im guna try and get some cortina hubs and fit some different calipers.