What T-case to match a th700r4

[idastang]

Hi, I am looking into changing my th350/203 for a th700r4. What I am not sure about is what year trans and t-case should I be looking for? This is for a 69 short bed with a 12 bolt rear and a dana 44 up front. The engine is a 327. My goal is to have something that will cruise the hyways a little better at lower rpms. I am runing 32s and not sure what the gearing is. Is there some way to id the gearing? I know the front dana 44 is from a 76 k5 blazer based on the BOM number. I not sure if I will be able to find a matched set together so I need to know what to look for in a th700r4 and t-case. Thanks for any help.