1) What Turbos bolt up to the stock exhaust manifold for a SR20DET? Any that can make 350whp?
That can make 350rwhp...none that I know of, but I don't know a lot about SR stuff...
I don't think you'd want to push a t28 (or even a t3 if there is an adapter for it) to 350hp...it'd just be blowing hot air.
Best bet would be a new manifold and a t4 or t3/4 hybrid.
2) Will a SR20DET bolt up to a KA24's Tranny?
Yes and no. It will not "bolt up" the the KA tranny will work with the SR motor if you get an SR bellhousing. I'm not sure what kind of work it takes to make that fit, but it has been done.
3) How much is a fair amount for a SR20DET (everything needed for the swap)?
http://www.unstable-hybrids.com
http://www.srswap.com
http://www.boostdynamics.com
http://www.mckinneymotorsports.com
Check those out...
4) What parts would be needed to run 350whp on a SR20DET (daily driven, pump gas preferred, but I have acces to some Race gas ~112 octane iirc)?
You definately don't want to have to use anything higher than 93 for daily driving. I don't know what all is required but you have to upgrade most everything to run 350 safely...internals will be fine for a while but I don't know how long they will hold up.
Check the above linked sites for more info.
Also see
http://www.freshalloy.com they have a lot of usefull SR information.
5) Are the 89-91 240's RWD? (I believe so but just to make sure)?
Yes, all 240sx's are RWD.