[Oliver Knuf]

At fist, a question back, what building year is your 1303? It's possible to adapt the complete 944 S2 front to the superbeetle, but you have to change quite a bit. I know conversions with the spindle from the 944 S2, but on the superbeetlesonly site, there's a complete conversion with the axle parts to the frame end.
The rear is easy to change, as you can use all the S2 parts, including the torsion bars, but in case of modifying the complete car to an adjustable spring setup, I would use spring plates with CNC-machined mounts, unibal mount in front and completely adjustable. There are different front and rear coilovers available. I think, we have three different front setups and two different rear setups. A complete race version is also available, with spring tension rates by demand and exchange springs, to work a bit on the setup.
Your fenders will be too wide with 40mm and 70mm, but when you use the complete new axle setup with rack&pinion in front and the aluminum rear IRS parts, then it would be good to be so wide. Hopefully you'll use the hollow original cup wheels and no copies, as these ones where to heavy for track racing.
Use at fisr the same master cylinder from the 944 and if you do it tricky, use a brake module to get more power on the brake from a Mini Cooper or something in that style. Mike Ghia, also a participant of this forum has a servo controlled brake on his beetle, if I remember that right. Ask him for pictures!