the 2.7 and 3.0 are completely different motors the 3.0 was a big redesign

 

very.
from what I know, the regular 2.8 can go as high as 2.9 when rebored.
the 3.0 can go as high as 3.2
the 2.7 is much better, it has thiker wall, so it can handle more power.
the runner is points opposite, but I think if the inake port at the end, it provide better power.