Well it really comes down to the year your getting.
If you get a 89-90 there is no bolt on turbo kit
if you get a 91-98, there are a belive 3 turbo kits all with drifrent stages
if you do end up with a 89-90 not all is lost, you can easly pic together a turbo setup. you will just have to pice it all together. and the hardest part is getting the turbo manifold, its either a custom job, or you can get a log style from
www.realnissan.com
as for the trubo kits for the 91+ there is a site that i like
http://www.enjukuracing.com/ that i belive sails them (not sure i havent checked if they still do) any trubo parts used for the SR besides the turbo manifold should be easily adapted to work with the KA also