S2 front bumper will fit straight on. Looks excellent, and they sometimes crop up on ebay quite cheap once in a while. Expect to pay 200-300 quid for bumper and grilles from VAG. Don't be tempted by replica parts.
As for other body parts, the only real difference an S2 had over a normal coupe or cabriolet was the front bumper.
In my opinion the S2 front looks more at home on a normal B4 Audi than anything.
The early 2.6 and 2.8 Coups and Cabs actually came with the S2 bumper anyway, but I see from your picture that this is not the case with yours.
You can get OEM clear indicators (the large ones next to the fogs), and fitting those along with clear side repeaters finishes the job nicely.
I wouldn't try to go any further with body mods - the design is beatiful as it is and anything that might look out of place will look out of place........if you see what I mean!
Not too sure about fitting Quattro running gear - I'd imagine it to be a very expensive job though, and not that beneficial unless you were running 200+bhp; which leads me to the engine........
It will be very hard for you to find tuning parts for a 2.8 V6, and therefore you'd end up paying alot of money to get the right parts.
The 5 cylinder engines were always highly regarded (I'd definately regard them highly), and there are alot more tuning options available.
It depends what you want from an engine. If you want a smooth 180-190bhp lump then stick with the V6 and I'm sure some headwork, big valves and a wilder cam would give an extra 10-20 horses.
However, if you're wanting something fast, then it is always going to be expensive. And do bear in mind that tuning engines of that age (be it a 1990 5 cylinder or a 95 V6) will never do the engine any good.
If you're loaded, I'd recommend the following:
Suspension overhaul;
Quattro conversion;
Rebuilt and tuned 5 cylinder non-turbo:
I've had experience with the 2.2 KV engine and also turbocharged cars of a much higher horsepower, and I have to say I much prefered the 5 cylinder. It just seemed a more honest engine. I wouldn't go for an S2 transplant personally - turbos can cause more hastle than they are worth, especially with an older engine like the S2.
You could easily achieve 210 - 220bhp from a 20v n/a 2.3, and I would have thought 200bhp was possible with a 10v n/a 2.2. But it's not just the peak power that makes the engine - it's the power delivery and torque. With the KV (10v) especially it has a nice spread of torque from really low revs, and this torque is put through the wheels the minute you put your foot down. Tuning a KV properly doesn't create a trade-off between low-end grunt/flexability and top-end power. You get the same engine, but just more of the creamy torque.
There are quite a few tuning options (I think I mentioned TSR in an earlier post).
TSR are one company that specialises in older VAG engines - 8v 1.6 Golf GTI mk1, 16v GTI mk2, older Quattro engines, etc.
They could fully rebuild and tune a KV from scratch; increasing capacity to 2.6, porting and polishing the head, fitting larger valves, a high-lift cam, blah blah, the list goes on.
But anyway, like I said, this would not be cheap!
Hope this helps.
