T5 is T-Mobile. They have less coverage than AT&T (C4) and are a little more strict on MMS and other nice features. AT&T is the preferred GSM provider for TF. A 64 SIM card has 64k of data and I think is enabled for new things like 3G, if TF ever uses it. The regular SIM cards are older and hold less data and don't support as much... apparently. Tracfone SIM cards don't work like regular SIM cards, you can't switch them out into different phones, they are tied to one phone - but yes, you can use them with any GSM tracfone.
I don't know where or why you would find TF SIM cards in bulk... are you by chance named Patty?