Some xA6x Celicas in Japan has these stock - Ra63s I think.
However, I'm pretty sure it's not legal to put that engine in an '84, as the engine is older than the car, and engine conversions have to be saem year or newer IIRC.
New Engines just have to match or exceed the emission standards of the engine its replacing, regardless of ages.
Find the factory emission specs of the 18R-G and the 2S-C and that will tell you if you can replace it.