I have used Google so much ... but what I REALLY want if I can get it is experience of people from a trusted source (aka this community)
Two things come to mind from your last post if you don't mind me asking.
1 - is ET35 the standard offset or is that only for the GTAs because I really want to keep the standard offset if possible. This is intended as a road car - not a track car.
2 - Why will fitting the GTA brakes be such a challenge? I am guessing that the mounting points will be different - or is one axial and the other radial? I wasn't actually planning on using GTA brakes as it happens because I wanted to have some bells made up to accept bolt-on discs, but I guess I could use the calipers off a GTA. I guess also that as I am planning to have my own bells made up that I can accomodate some difference in the alignment/adapt to suit with bespoke bracketry.
Do you know if there are any issues with the master cylinder. While I'm asking this - any ideas what master cylinders will give me a harder pedal? I find the stock one way too soft (and no, there is no issues with brake fluid).
Since you obviously found the brake thread where you will find everything you need to know(the callipers are exactly what you cannot use off a GTA, unfortunately), I will answer question 1.
I think standard GTA ET is 32, but the GTA has wider arches than the stock 156/147, which has an ET of 38 iirc. So the OZ wheel will stick out a bit more, being wider(7.5" or even 8") and having a smaller ET than stock.
Just in case anyone is interested, I have a spreadsheet I did years ago for a race car I was having set up problems with.
Given certain data, it will identify the correct balance bar setting front to rear. Parameters are
1 - wheelbase
2 - CoG height
3 - static weight balance Front to rear
4 - downforce Front and rear
5 - Master cylinders sizes for front and rear circuit
6 - slave cylinder sizes for each caliper (actual pistons diameters and number per caliper required)
7 - Rotor diameter
8 - mu estimates for brake materials (in case you are using different pads front and rear)
9 - Target deceleration rates (in 'g')
I think that is it. If anyone wants a copy, let me know, but I warn you it is NOT a user friendly document. It only took me a couple of hours to knock up - but it proved VERY effective. Having spent three meetings struggling with brake setup and being given so much duff advice by people who should 'know' I used this sheet to set up the brakes for the next meeting. It was less than a quarter turn out on the balance bar, so I reckon it is pretty OK. Similar situation when we needed a wet set up for that matter.
May not be overly useful for a road car, but you should be able to 'check' the options you have/are interesting in getting.