The 700/R4 has a 4th gear overall drive ratio of .70. This means that your 4:10 gears are equivalent to 2.88s in high gear. The 700/R4 gives you punch on the low end, and a decent cruise on the high end. The tricky thing about this trans in a specialize application is proper calibration of the TV cable.

With those gears, you DO not want to switch to a TH350. It doesn't have overdrive. Don't switch transmissions. The 700/R4 is a pretty darn good performance transmission. They came stock in a lot of Corvettes.

If your transmission is dragging the engine down when you let off the gas, then the converter isn't unlocking. That's not good.

It feels like my transmission isn't strong enough to spin my gears at high speeds.
I have NO idea what that means.