I'm not exactly a motor swap expert, but I can fill in a few of the blanks for you.
First off, x3 is the platform code for the 1995-99 Accent. (In Australia, this car was still called the Excel, just so you know... they didn't adopt the Accent name until the 2000 model year). x1 refers to 86-89 Excels and x2 is the chassis code for 90-94 Excels.
The platform code for the 2000- current Accents is LC.
Alpha is the code name for the Accent's motor. It was actually first used in the 1993-95 Scoupe, and starting in 1995, was used inthe Accent.
The Beta is the 1.8 and 2.0 litre used in the 96-present Elantras and 4-cyl Tiburons.
The Delta is the 2.7 V6 used in the Sonata and the 3rd gen V6 Tiburon.
As far as motor swaps go, several people have swapped Betas into Accents.
The Excel, and earlier Elantras (92-95) are Mitsubishi based cars. The Excel came stock with the 4g15, and I can't recall the motor code for the Elantra... I know they came with a 1.6 or a 1.8, depending on trim.
The 4g63 is the motor code for the 2.0 litre that was used in the Talon/Eclipse/Laser/Galant/2000GTX. It came either as a N/A motor with 140 hp, or as a turbo motor with 190-200 hp. The N/A motor is referred to as the 4g63, and turbos are known as 4g63t.
The 4g63 can be swapped into the Excel and early Elantras as well as into earlier Sonatas.
Generally, swapping a Mitsu motor into a newer Hyundai or vice versa isn't really worth it, for a number of reasons.
The Mistu motors were oriented differently in the engine bay, with the motor on the driver's side, and the tranny on the passenger side. Hyundai's newer, homegrown, engines were reversed from that, with the motor on the passenger side and the tranny on the driver's side. That makes it more worthwhile to keep the Mitsu motor swaps limited to older Hyundais, as they don't require as much custom work for the motor to fit properly.
As well, as far as Accent swaps go, the Beta is a perfect candidate... it gives a significant power increase, even if you leave it N/A; it requires little custom work to make it fit; and even though the Beta has never been sold as a turbo motor (unlike the 4g63), the Beta is a tough motor, with a strong block, and can be turboed reliably.
If I were you, I would buy an x3 Accent, (so far, I think there have been many more x3 Beta swaps than there have been with the newer LC) and find a good quality Beta motor (they can be found on e-bay fairly regularly) and do that swap. The Beta can be swapped in with the Beta transmission OR it can be used with the Accent transmission too, if you prefer.
Many other Tiburon/Elantra piece fit the x3 Accent too... the front brakes are one example I can think of right now.
That's pretty much the extent of my knowledge as far as this goes... I now open the floor to other members... particularly Rudy and 99mini, two members who have done the swap successfully. Due to an accident, Rudy's car was sadly written off shortly after his swap was done (it was a sad day here when we found out), but as far as I know, 99mini's car is still going strong. I'm sure they, and others (TurboHyundai, who has a GORGEOUS older Sonata with a 4g63t) will be able to offer some advice.
[Edited by stickshift on Mar 10, 2003 9:12 AM]