Good questions, but I think searching may help.
The rear (Nissan R200) is a strong unit. And aftermarket internal upgraded are plentiful. I think the R200 can handle a solid 6-700 ft lbs at 3000 lbs all day. The axles, well you might wanna upgrade those.
As far as power, you can make what you want. The Ka-T, and SR setups will allow for a nice 250-400 RWHP, an easy 300 all day. You can make more, but it cost a lot.
You can swap, RB inline 6 engines, V6's V8's, whatever you want really.
My car as it sits is about 2720 lbs at 430RWHP on a mustang dyno. Its kinda stripped down, but not too bad.
Check this out. (check out the list of build threads).
zer...sting