That's a good link - it's a fairly smart option that V8. If I was to 'think out loud' I'd suggest either a larger capacity NA engine like this (and the ITBS make for better throttle response and a wider power band, which is a HUGE deal for this sort of stuff) or if I was going for a smaller engine, I'd run a supercharger rather than a turbo if possible. The instant boost/power is far more important than peak power which is where the turbo would shine (peak power that is))...

Thinking further out of the box, I'd also wonder if anyone has tried running an auto. A 'normal' auto slushbox would have issues, esp with convertor selection - loose would help it spool off the line so you could have it in the power band for the first corner (not as important with a supercharger or big NA engine of course) but wouldn't be as good for backing off and flooring the throttle immediately after, it'd actually 'try' to hook up and get traction a lot more.

Never mind though - this thinking out loud was for a reason - it's a little bit of overkill for a small 4cyl, but for something else there's another option that has been used in dragsters (less and less recently, but they are around) and it comes under various names. Some people call it a clutch-flite. Basically what it is is a specially modified chrysler torqueflite automatic that has the oil pump drive modified to be slightly differently driven, and the input shaft is no longer fitted in a torque convertor, but into a 'regular' clutch plate that you'd normally see on a high performance manual gearbox. Then the valve body is modified to be full manual (d gives you 3rd, 2nd selects second and L or 1 selects 1, no matter what road speed). Then you hook that to a ratcheting shifter (the quickshifter, megashifter, whatever brand you like) and you then launch like a normal manual, but once you are going you just snap the shifter forward a click to get 2nd then again for 3rd, or back a click to go back to 1st. Basically you can do instantaneous and reliable shifts in either direction without having to come off the throttle or pushing the clutch pedal at all, so lightning shifts (and with a bit of practice, left foot braking, so you never have to move your right foot away from the accelerator pedal.

I truly reckon there'd be some real advantages to that, and it'd get around the one thing where autos aren't as good, engine braking and response immediately after you go from engine braking to full throttle. A direct link and reliable shifts, All good imo. And whilst a clutchflite setup wouldn't last on a streeter, it'd certainly handle a drift competition. Even more ironically, since there is no torque convertor, 90% of the heat generated by autos comes from that, so it'll run cooler and last pretty well in such an application.