Cant say I have seen a KB laser turbo but I know on my KB laser runaround that the carbie is exactly the same as the 1200 type (the only modification requirements requiered to fit it to the 1200 manifold is 1 hole needs to be drilled for one of the 4 studs! If you look at 1 you will see what I mean!)

I used to have a customer that had put the daihatsu carbie and turbo setup on his 1300 corolla! ( he was a mechanic that knew about carbies and I am sure he resized the jets!) The car was very zippy around town due to the small turbo! (Later he put the fuel injection and a bigger turbo!)

Regarding the fuel filler neck - I think I understand what you mean! but there was no need as the pressure is in the fuel lines not the tank!( I don't think I would like a tank that was beeing pressureised!)
- This is what we used;
1 VL Commodore Fuel Pump,
1 Malpassi Rising Rate Fuel Regulator (for carbie not injection! ),
and 1 fuel return line back to the tank!

It works like this - fuel pump pumps fuel to the regulator ( the regulator has an inlet from the tank, and outlet to the carbie, a returnline to the tank and a vacuum/boost line from the manifold!)( this VL pump is used due to it being able to produce hi pressure and flow!)
When the vacuum/boost line is giving vacuum the regulator will send around 3-4 psi fuel pressure to the carbie ( pressure is adjustable!) and the extra fuel back to the tank through the return line!
When the vacuum/ boost line is giving a boost signal the regulator closes the return line enough to give the carbie more pressure than there is boost and still enough fuel flow!

The regulator is required because you need the high pressure fuel for boost and when there is no boost being produced the carbies needle and seat can't handle to much pressure!
Go the Datto had another setup which he has talked about you might like to go back and check it out!

*** One other modification that was done to the boosted carbies is we made a brass bush for around the fuel plunger to help seal boost and fuel loss from here under boost! ***

Also chokes are for pussies! lol! nah but really we took the chokes out as they looked to much like a restriction!
But even if you did use one I couldnt see it being any different to sealling around the accelerator or the fuel line!