Probably the best head you can get is the 6cc Fred head and you can get the genuine Fred head straight from crmachine.com for like $39.99 which is cheaper than the knock offs...
For the ignition, the stock unit is still one of the best performers. The HD lightning is an excellent unit when it comes to reliability and it might smooth out the engine a little but don't expect any huge power gains with it or any other aftermarket CDI.
For the carb, the stock NT and the NT speed carbs can both perform very well and if you want a better carb, the Dax RT carb works really well and so do the floatless type carbs like the Walbro or Tillotsons but they're not a bolt on affair... They do work good when you get them attached and tuned proper tho. My favorite carb tho is the Mikuni VM18. The 18mm Mikuni will give a noticeable performance increase but still have good street manners. Anything larger will work but not be as easy to tune and may not behave too well for just cruising around. Reeds work really good folr making better torque and power but again, not right out of the box... you'll need to cut a window in the piston and add ni a boost port, then they rock.
One of the most effective ways to get a big power gain is by doing a port job on the cylinder by widening the ports as well as raising the exhaust roof, intake floor, and cut out about 5mm from the bottom of the piston skirt on the intake side... porting is a huge subject since it will determine how much more power is available as well as at what rpm range the power comes on strong at. This is also one of the easiest ways to convert a good cylinder into a paperweight tho so make sure you know what you're doing before ever grabbing a dremel. There's a lot of info on porting and port timing in here in the high performance section as well as a lot of help available from members.