I was told that a garret gt2871r would fit onto this manifold. Is this true?

 

Since it is flanged with a T2, yes the turbo can fit onto the manifold. The rest is up to you on making sure it is properly clocked and fitted to that manifold.

 

so assuming that it does fit I will have to have a new downpipe made or will the elbow that comes with the greddy (restrictive one) fit onto that turbo?

 

the DP opn the greddy kti is different, but with that gt28 you should run a full 3" exhaust system if your going to do more than like 9-10psi.

if your going for liek 9-10psi then you could get away with 2.5".

 

so it will fit the manifold but Ill have to make a new downpipe then correct?

 

i am considering the same thing...
the turbo and the dp will fit. the dp and flange are pretty narrow. 2" i think. check for clearance issues... the turbine seems to have room, but the comp is tight... maybe the 50 ar comp fit easier. wutever you do, let me know how it turns out!!!