I know this thread is really old. But I wondered if you had gone through with the .60 over bore. if so how did it turn out, did you have any problems? I just had this done to mine and paid a good amount for it to be done and I'd like to avoid any problems I may have.

 

I only have 4 k on my build but .60 over worked great for me. I read enginbldr did .60 over in his sons truck but looked carefully for a block that was stout enough to handle it. Paired with the 268 cam this thing rocks on the hwy. After gearing it down it will be perfect fo what I wanted. I don't need to go 100 mph...

 

I've got a bit over 3000 miles now on mine with a 270 cam, 60 over, shorty header and 38/38 Weber and absolutely not issues. Fast for a 22r!