iPhone 3GS 3.1.2 firm 5.11.07 BL 6.4! Upgrade?

[ElCapitan737]

Hi,
Sorry for this noobie request but I have an iPhone 3GS on 3.1.2 with firmware 5.11.07 with boot loader 6.4 jail broken and unlocked with blackra1n.
Please tell me how to upgrade to iOS 4.1 or 4.2 where it can still be jail broken and unlocked on windows. Also needs to be hacktivated as I don't have an ATT sim.
Is it possible to preserve the baseband?
should I use snow breeze?
Feeling a little lost with all the conflicting and confusing information.
Your help is much appreciated.
Thanks.

[Simon]

You can use snowbreeze but it may give you issues with youtube (amongst other things) if you hactivate it. You will also need 4.1 SHSH.

[Mes]

A customer firmware load (via PwnageTool and/or Redsnow and iTunes) preserves the baseband. SAM will activate. PwnageTool is the best, Snowbreeze has not been updated.

But first, download Tiny Umbrella, connect iPhone, select save all. Veryify what FW versions you have SHSH blobs available.

The Firmware Umbrella - TinyUmbrella

Next use iDetector and see if you have new (or old) bootom. The latest iOS 4.2.1 jailbreak is tethered ... unless you have a Mac and want to risk beta redsn0w software.

Report back. There are many stickies in the MMI Redsnow/jailbreaking forums with extensive information about when/where/how/etc/etc/etc. Good reading.

[ElCapitan737]

Thanks for the prompt replies.
I have shsh blobs saved for 4.0, 4.0.2, 4.1.
Boot loader is 6.4.
What would be the best way to upgrade to 4.1 with untethered jailbreak, unlock and hacktivating on windows while preserving the baseband?
Thanks again for your help.

[Simon]

Just use snowbreeze to make a custom 4.1 and restore to that.