The Optimus T and the Optimus One are essentially the same phone. You can use any Optimus One ROM. I have tried openOptimus and devoid/Franco ROMs. They are both great. Found them over at XDA. Optimus One, P500 Android Development - xda-developers
The only problem is there is no T-mobile wifi calling with a Optimus One ROM. However, there is an unofficial CM7 port for the T-mobile Optimus. It is a VERY new ROM. (I have not tried it yet)
Unofficial [ROM] Cyanogenmod 7.0.3 (Android 2.3.4) Gingerbread for Optimus T - xda-developers
The only problem is there is no T-mobile wifi calling with a Optimus One ROM. However, there is an unofficial CM7 port for the T-mobile Optimus. It is a VERY new ROM. (I have not tried it yet)
Unofficial [ROM] Cyanogenmod 7.0.3 (Android 2.3.4) Gingerbread for Optimus T - xda-developers