Let me summarize all this crap...
Those wheels you want to run are 5x120, and yes, I agree, they look great. You would need a hubcentric spacer to go from 5x114.3 to 5x120. You can't get those spacers in 4x114.3 to 5x120. I looked into this two years ago for these exact same wheels, from a Formula Firebird.
What is more, when you use spacers that change the bolt pattern, there is a minimum thickness that will work for them. Usually the minimum is THICKER than the minimum for a hubcentric spacer that goes from same pattern to same pattern. This is because it needs to maintain metallurgic integrity between the bores for the studs. So what you are left with is a low offset wheel, which will portrude from your front, and adding to that a 3/4" spacer (approx.) thus shoving the wheel even further outward.
This doesn't take into account that you will have to switch to SE five lug hubs on the front and back, because as I said, I wasn't able to locate 4x114.3 to 5x120... only 5x114.3 to 5x120. So there's a lot of work just to stick out vato-style, for wheels that, while they look nice, they also happen to look like literally a dozen various mesh knock-off wheels available in both four and five lug 114.3 and in offsets more palatable to our cars.
So the spacer idea is a flop.
Slotting wheels is fucking retarded, and I won't even consider the notion worthy of more comment than this one sentence.
Filling and drilling wheels is largely limited by the design of the wheel, of which MOST (not all) mesh styles do not provide adequate space to do so. This will also sometimes lead to cracking of a wheel, again depending on the style. And again, mesh wheels are not very tolerant to redrilling. Most wheels that get redrilled have a more solid construction to them. Even then, it's a total waste of time and money to make a wheel bolt up that will poke, when there are (again) many mesh knockoff options that look similar (or even the same) as these Firebird wheels.
Further discussion of this is, much like the idea of slotting, retarded.