I hear you on the over-boosted road feel.
No I doubt you can do it in frame,at least not without the factory nut-tool,and you would have to remove the column; but the box drops out the bottom pretty easy, even with Headers. Watch out it is surprisingly heavy. I only added 2springs the first time and a week later I added a third. IMO it's best to have the box in a vise, but even that is optional. While it's out this is a good time to put new seals in it.
The FSM tells you to use certain specialty tools , but I got away without them. Honestly that box is real simple. Once it is on the bench, you can have it apart in minutes.
