update 4.0.1 to 4.1 then unlock?

[bikedogrun]

I'm about to inherit a 3GS running 4.0.1 with 05.13.04 baseband. Good so far...

What I'd like to do is upgrade to at least 4.1 but perhaps 4.2.1 (?) preserving that 05.13.04 baseband so I can then use Ultrasn0w to easily unlock without being on the dead-end (for now) 06.15.00 baseband.

Is there a fairly straight-forward tutorial on here somewhere? I am self-sufficient enough to follow directions if pointed to a good set of directions ...

/BD

 

[PsstGreek]

If you have access to a Mac you can use PwnageTool to either go to 4.2.1 or 4.1.

PwnageTool lets you create a custom ipsw and preserves your current baseband to unlock.

To go to 4.1 the SHSH would have to be for the 3GS. 4.1 will be an untethered jailbreak. 4.2.1 will be untethered for the old bootrom 3GS and tethered for the new bootrom 3GS.