supercharged probably around 250-270bhp 240ft torque
turbo depending on setup and which one etc 300bhp +
In either case a complete engine rebuild and uprated internals put in i reckon a good 270bhp charged version could be done for 1.5 k possibly 
Don't necessarily need uprated internals. Standard ABf on stacked gaskets can cope with 300+hp and 280ftlbs torque. Mine on last rolling road check put out 260ftlbs of torque and 240hp. Has more now but haven't had it confirmed yet.
Depending on the supercharger. Cheaper M62 eaton is the common one. 230hp/ 220 ftlb torque. or there abouts. Just cant stand the whine.
When working out costs. Think of a figure and add half again.

Amazing how all the little things add up. Also depends on the quality of components used including whether you have all correct saftey devices and gauges etc.
People talk about power figures. Has anyone driven a properly mapped 220 hp car with torque to match? You may find its faster than you think. It all about the torque.
How much do you want to spend?