I know nothing specifically about the KLX FI system, however, I wonder where the fuel pressure regulator is located. Most all FI systems I've messed with require a pressure regulator somewhere. In a full loop FI system on a motorcycle, I could see them being able to have the regulator in the tank while in most cases it's located on the engine or right near it. I'm just mentioning this to insure you address the regulator in case it's in the tank when you remove the factory tank.

Ooops...I see you mentioned a regulator in an earlier post, so you're well aware of the consideration. Carry on.:D

The regulator / pump / and fuel level gauge / warning light are all in the tank in one unit.
That is the other problem i would face if i went down that route , does the ECU take signal from the level gauge, if so how do i over come that issue also ,,

Do you have a wiring diagram? You could trace out the route from the fuel gauge to its signal source. That said, I can't see the fuel level tank sensor having any functional impact on the operation of the FI system. If it's wired through the ECU, I'd guess that was a matter of convenience rather than a requirement for the ECU.

Yes, It looks like you are right, the sensor is just a reserve switch not anything to do with the EFI. The pump has a positive and negative, the third is the return from the switch,

Should be able to do away with the switch and use a reserve tap.
Still trying to find a small pump and regulator.

FYI

The manual states that if the fuel filter is block you have to change the whole pump unit , Crazy. LOl

Yeah, it's surprising that lots of factory FI pumps and their hardware are not very user/owner friendly for service or repair...automotive or motorcycle...and often as expensive as heck.

While it is possible to adapt a pump/regulator to work with the carb tank, making it a functional reality is the real question. Using an oe CV carb(there are plenty of used out there) would be the most economical.