Those parts depend on what you're looking to do with your bike.
The fuel pump saves weight and electrics and I'm very happy with it. However the stock one is easier to handle with when you need to do some carb work
The koso tachometer is sth I definitely wouldn't fit again. I fitted it as it was necessary for the street use (tüv) and I couldn't run the stock one due to the rims
I would go with the zxr one or get sth like the aim mychron5 or similar
Here's a chance to show off your zxr400, so get them digital cameras out and show us some piccies.Rebuilding your bike or modding it then let everyone in on it.