Greddy 1.6l on a 1.8L?
 

Is the only difference between the 1.6l kits and 1.8l the manifold? Im looking for the cheapest way to turbo my 2000 ls.

The manifold won't fit. The crossover isn't the same. The FPR won't work with your returnless fuel system. It's basically worthless with your '00.

I say build a kit with BEGI mani/dp/IC & pipes then use megasquirt for your engine management unless you can build some things yourself.

Buy a 2nd hand 1.8 set...probably cheapest route...
Or doy, HKS mani with Begi greddy dp is a good start.(ask if begi welds a t28 flange on it).