ITB 3.0 all the way if it fits your budget. At that point might as well make short stroke 3.2 (98 x70.4). Your 901 tranny might not be happy.
With stock 3.0 CIS induction and cams you are limited on how much power you can make. Since you asked
dyno below is 2.7 Mod S cams vs 3.0 with CIS. 3.0 Engine had 78 big port heads, later 9.3 to 1 pistons and headers. This 3.0 engine was from PCA stock class race car so limited in mods that could be done. I have dynos from several top stock class 3.0L engines and they are all about the same power. This was on the same dyno but different cars 2.7 was in 914 and 3.0L was in 911SC.
on 3.0 with better intake you can add about 15-20HP over CIS on big port 3.0. That was result with two similar engines one with 3.2 Carrera intake and one with carbs. Add pistons and cams for even more.
john