An OEM replacement Motorcraft from Ford is the only way to go on a TFI Module. All others just don't seem to last. And definatly don't buy a auto parts store chepo model!
I installed an MSD Pro Billet Distributor a year ago on my Mustang and it came with an MSD TFI module, and it lasted a whole month before it went TU! I put a Motorcraft from Ford on there and no problem since.