There have been a lot of posts about this at one of the biggest iPhone hacking websites (
http://hackint0sh.org/forum/forumdisplay.php?f=136).
The answer is that it's not certain what you would get, but that it's very unlikely you would be able to find a non-1.1.2 iPhone. Apple seems to be very good at changing firmware versions everywhere very quickly.
There are rumors that the dev team will have an unlock for the new bootloader soon - like in the next 10 days or sooner. They cracked the secpack - it's just a matter of time. Then it's just a matter of downgrading the firmware to 1.1.1, going to jailbreakme.com, installing the new SIM unlock tool for the new baseband firmware, installing "oktoprep" and upgrading back to 1.1.2.
Alternatively, there's a TurboSIM unlock for 1.1.2. But TurboSIM isn't cheap. There are plenty of posts on TurboSIM in the URL at the top.