I'm running a freshly rebuilt engine , 31's, 261 C cam, chromoly connecting rods, and have 4.56's. I can run ,70 all day long in 4th gear below 4k rpm's. I will be interested in seeing how it does on my next trip to Salem. I took my last engine down there before it snapped a rod. I still have the stock exhaust and my timing is set at 8* BTDC.