ECMLink.com can answer the question about using an Elantra ECU from 1992-1994.5 <- the ECU changed half way through 1994, and the connectors no longer looked like the 1987 JDM - 1994 DSM style.
Source a 4g61t Eprom - that info is also on their site, but using a 1990 DSM turbo Eprom ECU, is your best choice.
Be advised your pistons are not made for a boosted application by design they have smaller ringlands where the piston rings sit.
You can add a few wires to make the MAF wiring compatible from the ECU to the MAF connector.
What supporting mods are you going to install into the car to make up for the new found power and requirements to support a turbocharger and it's fuel and regulation demands?
You need to upgrade the fuel pump, fuel pressure regulator (rising rate FPR), fuel pressure gauge, turbo ECU, wiring, turbo, exhaust, injectors and MAF, oygen sensor and wideband, and tuning depending upon how far you go with it.
IF you put 4g61t pistons in the car and rehone the bores to match, with new high quality rings, you will have the same crank shaft treatment on that Hyundai crank that the stock 4g61t or any mitsu motor had from that era - nitrided.
I don't suggest boosting the stock NA motor, ever. When you get a turbo motor in there, then you can start modifying the system to support a boosted application.
The only difference in that 4g61 motor, is the lack of turbo style pistons and rings. It has the same blocked off balance shaft setup as the 4g61t motor, and only minor bolt hole locations different on the side cover, from that of the original 4g61t motor. I was using a 4g67 timing cover on my 4g61t for some time, and it was a near direct fit.
There is a lot of little things that will be needed to make this work, and I have somewhat omitted from the wiring, connectors at the MAF, and ECU's, because I am not sure how far this project is going, and in the correct direction. Forgive me if I have assumed anything incorrectly, but small posts without a back story, can lead to answers like this and I only want to see people do this correctly, the first time.
Anywho, that is my opinion.