I like it, post up some pictures; don't be put off by how your car looks right now, its a nice thing to have before and after. As for Nort American V8's I have no problem with them at all, over all they are superior in every way to overhead cam V8's because they are more compact and you get more power per LB of weight assuming you are going with alloy aftermarket heads like "AFR", and aftermarket alloy intake manifold.
Overall the torque and power you can produce with a domestic V8 is superior to anything that can be done with the UZ Toyota or even the modern V8's produced by Toyota because the aftermarket support is utter trash when compared to that of the Domestic V8. Sure the new V8's are rather cool and its nice to keep a Toyota all Toyota, but what really counts is that you are having fun and you enjoy the car you're building.
As for the option of the i6 2JZ, well the V8 is gonna be less $$$$ for the power, and with the V8 you can move the weight further back in the chassis.
I you are going Ford and you want power, and not fooling around with lame power you may consider checking out John Kaase Racing; link >>>
http://www.jonkaaseracingengines.com/
John is the real deal; he builds heads that you can damn near drop on a stock 5.0HO Ford and build 500 HP at the crank with a 9.0:1 Compression ratio meaning you can run pump gas with 500 HP at the flywheel / converter
naturally aspirated.
Furthermore, they do well on boost; the sky is the limit with real parts. Do not be put off by the price of those P38 heads, they are street car head and they are 100% complete. They include all the components you need to make them go; when you compare the pricing to those makers like AFR; the total installed price with the same quality gear is roughly the same, the difference being is that you have Cleavland style heads for a small block Ford that breathe well down low producing mad torque through the whole RPM range, unlike large port heads produced by other aftermarket companies.
If you are put off by the price of those heads and its just outside your budget, the next best deal is AFR, they make damn good heads. If you want any kind of low RPM torque then consider the 165CC heads, they are the best bang for your $$$$, they do build other larger CC ports but the power is only any good mid to top because they are windsor style heads.
As for Supra suspension there are some sources for springs and coil overs, the forum has a few really good write ups on that stuff.
Not sure what kinda racing you are interested in, but you might consider building a C4; they can hold the power from a big block if done right; and they move more power to the rear wheels while being lighter..
Important: buy a trans cooler if you are going to run and Auto trans; it will save you much pain in the long run.
Lastly; V8 powered anything is usually cool as hell, I don't consider your project blaspheme.