you will need new heads to get all you can out of the 347... now if this is a daily driver i would do the following
coast high performance 347 street fighter gt stroker kit (you don't really need fully forged internals due to the fact that the cast stuff will hold about as much horsepower as the stock block will) the stroker kit will come with everything you need.
http://www.coasthigh.com/Assemblies/Ford/ford_347.htm
the gt40 heads are going to be holding it back a ton so i recomend you get AT LEAST some edelbrock performer RPM heads (2.02/1.60 valves) but you can go anywhere from some afr 185s, 205s, trickflow highports, victor jrs, etc etc.
the gt40 intake manifold is basicly the same as the cobra manifold and you CAN use it, but i'd recommend a trickflow street heat, track heat, r series manifold, edelbrock performer rpm or rpm II... it's really up to you and your personal prefrence.
you'll need to machine your block, and it's in your best interest to purchase a 7qt oil pan, a better waterpump, and an aftermarket aluminum radiator, good fan, low tem thermostat, from what i've seen the 347s do tend to get hot. also longtube headers are good 1 3/4" - 1 7/8" headers, you can use your stock alternator, power stearing, a/c, fuel rails, etc etc, you'll def need larger injectors (at least #30s) and a larger matching mass air meter 75mm or larger and at least a 70mm throttle body. i'd recommend a custom camshaft but you can call places like comp cams, crane, lunati and talk to them and they'll recommend an off the shelf cam. Anderson makes great cams too the N-412 has a good idle and makes good power (
http://www.andersonfordmotorsport.com/) you also need some 1.6 or 1.7 roller rockers (you might be able to get these off your 345 GT40 motor i'm not sure what comes on there. gears, exhaust, tune, etc.
you're looking to spend around 4,000 dollars or more depending on that you do.
