Your tail shaft angle of 2.9 degrees is good, no need to cut the tunnel or try to raise it. The problem is you pinion shaft angle of .9 degrees down. With this current configuration, the driveshaft has a "speed up , slow down" phase. It gets worse the more the suspension compresses. A link below will show you what I mean. What you want is to get the pinion angle to mirror the tail shaft angle, but in the opposite direction. So you will want to get the pinion to be 2.9 degrees up. There are shims you can buy to angle up your pinion, these get placed between the leaf spring mounts and the mount on the axle tubes.


https://www.youtube.com/watch?v=Idk3BVDVHq4

Pinion angle shims... https://www.summitracing.com/search...rder=Ascending&keyword=angle%20shims