Two things:
1. You really need to get some full throttle quarter mile passes, as finish line mph and rpm will tell you a lot. For example you’ll be able to calculate the correct rear gearing. Comparing ET and mph you’ll be able to compute converter slippage. Without knowing these numbers any converter or gear changes are a crapshoot. Also, running high rpm “just because you can” is not really what you want to do. The dyno sheet tells you what you need to know. Shifting a couple/few hundred past peak power will likely yield the best performance, so spinning it to the moon won’t help unless you have a very flat power curve and it allows your rpm after each shift to fall back into a favorable power range.
2. As others have said, the 60’ is way off. My old car would 60’ around 1.47 and it was an 11.0’s car (also an E-Body at 3,200 lbs. race weight, small block). Right after getting some baseline full throttle runs this needs to be the number one thing to focus on.
3. OK, make it three things. Rather than changing rear gear, go to a taller tire. If you can borrow a set of 14x32 would be a good test to see if that’s the direction you need to go.