Camshaft Questions

I am considering a new camshaft in my 91 5.0 with the 4 speed AOD trans, I purchased gt40p heads, and a gt40 intake, 75mm throttle body and EGR spacer, and 24# injectors, what would be a good cam for a daily driver, that sounds mildly aggressive and will still give me gains? This is my first engine rebuild and am not sure what i should be looking for. Someone recommended the cam from an interceptor would that set up work? or is there a better option for my 5.0? Any help you can offer would be great. I as considering an E303 cam but is said for manuals only, why is that?

Stock torque converter, ECU, gears, ect ?

Either a Comp Cams XE264HR (part number 35-320-8)
or
XE270HR (part number 35-324-8)

http://www.compperformancegroupstore...Code=F50CEFIXE