67 chevelle pinion angle ladder bars
 

I have a 67 chevelle with ladder bars. It has a vibration at top end of 2nd gear and lower end of 3 rd gear then goes away at high end of 3rd gear. When checking the pinion angle I found the driveshaft angles up to the rear end from the transmission. The car sits fairly low. Was just wondering if I should still set pinion parallel to trans angle but tip pinion down 2-3 degrees since driveshaft goes up instead of down. seems to be close now but still vibrates. Don't know if I should tip it down more or what. I am going to have the balance on the shaft checked but since the vibration goes away at higher speeds seems to be an angle problem. Any help with similar setups would be greatly appreciated.