Wanted Infor On Alum Blocks

Hi Wanted To Know What Is The Difference Between Tfx Kb Bae Blocks. Which Is Better And Why Are Alot Of People Using Tfx In Alot Of Nitro Cars. Asking Because Have A Chance To Buy A Tfx Short Block Used For Nitro. Can Some One Explain And Offer Good Advice On Wheather I Should Buy A Used Nitro Short Block. Thanx