A simple swap takes $2000 by the time you are done, if you do all the work yourself, have the tools, time and space, and make good choices on where you spend your money. To do it nicely you might want $3000. If you have a front clip of a supra turbo of compatible year it helps, but you still will need some parts new. To build it with new internals and machine work, add another $1500 minimum, easily could be double that. To add mods you can count on another 2-4000. So if you don't have parts car, time, mechanical skills, tools and $2000 starting cash, I don't think you should attempt it. Sure there are a lot of ways to reach your goals, all well documented on this site and others, but to do it the way you say you want to, it's not a cheap hobby. I would think that the least expensive way to get a 450hp supra is to buy one already partly built, if it hasn't been screwed up, and finish the work. Or at least start with a turbo supra in good mechanical condition and mod that. If you get a nice car to start with, you may not need to rebuild the motor at all to meet your goals. An NA supra is a beautiful thing too, and spare parts are plentiful, so maybe just stick with what you have and fix it up nice?