What is 993 RSR head stud torque?
 

not sure if they're different than stock 993 (but don't know that value either).

If the stud is of the all-thread varaity it would be 30nm + 90 degrees. For some reason the same stud in the GT2 racing engine was 30 + 120 which was and is amazing to me.

regards

they're definately not threaded all the way down...

http://forums.pelicanparts.com/uploa...1181077525.jpg

That is fine, the originals are all thread but that is not necessary at all.
In your case 25 fps should do it with a lilttle lube, oil or such. With the bigger bores I favor putting the heads on the barrels and the cam tower on "dry" with a few bolts to fasten and index the dowel pins between the heads and tower, then torque each barrel individually to secure the big jug squarely.
regards