I assume you are putting a 9" in. I also assume you are seeking advice based on personal experience. A third assumption necessary is the operating range of your 347, 2000-6000 rpm; probably peaking power around 5800 with a sweet spot from 3500 on up.
That being assumed, with the 5 speed, you need at least 3.50 gears. Personally, I think 4.11 is the maximum for any regular street use, even with the 5 speed. Personall, I have a 306 with an E cam and am running a 5 speed with 3.50 gears and it is just fine. Sure, 4.11's would get me down the quarter quicker but I don't go to the track often.