1981 3.0L Rebuild
 

I've been reading How to rebuild and Modify Porsche 911 Engine. I've finally decided what my rebuild will consist of
JE Pistons (95mm)
3.0L Nikasil
3.0L Crank
964 Cam
CIS
3.0L Heads
@ Ratio 9.8.1
But I also like the following minus the the carburetors since you need high octiane gas and several more fuel filters I'll stick with the CIS for now

JE Pistons (95mm)
3.0L Nikasil
3.0L Crank
S Cam
CIS in place of the Carburetor
3.0L36mm ports Heads
@ Ratio 10.1
Will work or is my first option the way I should go.

I have 1981 Porsche 911 Targa

Thanks In advance

The main thing I'd offer is:

1) CIS cannot tolerate cams with much duration or narrow lobe centers. That means 964 cams are the limit.

2) CIS won't safely support the CR's that you are considering since you cannot richen it up sufficiently.

3) Be careful about using higher CR's with CIS-compatible cams as that generates high cylinder pressures at low RPM. Twin-ignition is a MUST for such configurations.