After looking at the photo of your dragster, you might consider moving the fuel pump & filter to the right side of the car and putting the bottle on the left side. The bottle doesn’t have to be perfectly centered, you will already have the weight of pump, filter, & hoses on the right so a little to left of center shouldn’t effect anything. Will the mount & bottle fit under the body and still set at an angle?
As for which single pipe in a set of zoomies to install an EGT sensor, that will depend on intake manifold flow characteristics from cylinder to cylinder and every intake is a little different, among other things. I’d suggest just going with the manufactures recommendations. Using Bruce’s example, with your car making about 400hp now & running 9.5 - 9.6 ETs, just a 75hp hit of nitrous should put you into the 8.9s. I think NOS is a good idea, I’m wanting to try some later this year myself:)