If your not changing the cam your TQ curve is going to be pretty much the same after porting. Maybe in the 5200-5800 rpm area you'll gain a little. But not to awful much.
What I'd suggest is just removing about 1mm of material on the intake side and then porting the exhaust side to have a constantly growing crossectional area. Take about 1mm off the ID of the seat and then continuously grow the port from there.. and matched to a set of headers. Prefeably stepped headers.
That way you'll reduce the delta P accross the head and maximize available TQ in the midrange.
Also, since your not boosting the motor and won't really spin it higher than 6k I'd just use OEM stock valve springs and OEM stock valves. They are about the lightest components you'll find. And they'll work fine with a 1mm ID cut. Maybe give the valve a 3 angle job if you'd like.
Besides.. if you want to spin past 5800-6000 your going to need to balance the bottom end. So you might as well just maximize the stock setup for mid range TQ.
But hey.. what do I know?