Yep thats right mate. I screwed the bottle to my sub box.
If you dont want to use the rear screen washer you can unplug the connection between the hose and jet on the rear window then connect the new washer motor to the hose that goes under the roof liner to the passenger arch. There you will see the line from the original bottle go up towards the bonnet and the line from the rear washer jet going to the boot. Just connect the line going to to the boot to the line going to the bonnet and that will save you having to route a line down the car.
But you will need to snip the old motor wiring and run come cable to the boot from were the OEM pump was.
There are 3 cables going to the old pump 1 earth and 2 lives, or is 2 earths and 1 live (1 for rear windscreen and one for front) play around testing which ones is the live and which ones is earth with the windscreen switch so you and use the OEM switch on the stalk.
Best Way I found when having a play around is just put the new washer motor (that uses 2 connections) in the engine bay and keeps swaping the wires over unit the motor activates. Then you know which 2 wires it is that you need to run to the boot.
I remember there being a problem using a voltage meter, there is something really odd with the system in the Supra.
Hope that help, If you need anything more PM me on FB dude.
This is the kit I used
http://www.ebay.co.uk/itm/160186-NEW-UNIVERSAL-12-VOLT-12V-WINDSCREEN-WASHER-BOTTLE-KIT-PUMP-JETS-SWITCH-/282152585487?hash=item41b19ac90f:g:cisAAOSwLVZVwnn-