I think the speed limiter is set at 130. I have had mine up to that when it was stock, as well as after RC1... the latter gets it there faster. It may go a bit more, but there is only so much road before I had to slow back down.
Assuming the speed limiter is NOT 130 (but I am pretty sure it is), it should be able to pull until redline in 5th if you had enough road. It takes a lot of energy to move a car that fast due to the drag of the air. I forget what the formula is, but as an example it takes more than twice the energy to move at 100 than it does 50. And 150 might be something like 5x the energy or something substantial.