Normally I wouldn't reccomend a T5 with a v8, but your 347 is only good for about 205 HP. A t5 would give you OD, as would an A833. The A833 will require some machining of the bearing retainer to fit the bellhousing. For what it's worth, I have a NV4500 behind my 1959 Pontiac 389, bored and stroked to 447, in my 1959 gmc 1/2 ton.

Transmission reccomendations are hard to do without knowing how you plan to use your truck.