Root HTC Magic 32a and b ?? confused

hi all, i'm new to this and have an htc magic branded t-mobile. Its unlocked and i have been following the xda developers guide to rooting. I did the normal thing by pressing back and on button to get the screen that tells you the model and it says 32b.

Then on rooting the rooting program said it as a 32a and it failed when backing up using the 32b file. therefor i used the 32a file and it backed up succesfully.

My query is now what do i do to flash a rom to it, do i use 32a or b as i dont want to brick my device.

Any help would be appreciated.