A guy on this forum - @Blaeven - has done the conversion to his gen2 Liberty. I'm not sure of the exact cost, but I believe it was somewhere around the $13,000 mark using a late-model EZ30R (which has AVCS, which was not included in the earlier gen3 EZ30's).
To me, this is just pissing away money when you could go with a turbo halfcut which will have more power, and more potential to make power.

To answer your questions though, every EJ and EZ series will bolt together with every EJ/EZ series gearbox, and they all share common mounting points. There are some small snags with using an 8-bolt gearbox with an engine that previously mated to an older 4-bolt gearbox, but they are easily fixed.

I have to admit Aek I considered the H6 conversion the first time I drove Dylan's car. I wasn't keen on the lag... Not really sure why now, it's great fun

Fast It's a great engine, a vast improvement over the 2.5L. I can sit on 4000rpm without even realising it. The brake lights were actually working, but both bulbs had blown... Go figure The only electrical problem now is the climate control isn't working, which I think is just karma for picking on Dylan's lack of heater or air con.

piper26 for some background I've just put a v7 STi engine in my gen2. If lag is what you're worried about, you just learn to drive around it, it's really not an issue.

Not hard and it doesn't have to be expensive. Bolts in to the stock cross member. Transmission bolts straight up. Same with any conversion for a Subaru the wiring is the hardest thing to do. Everyone uses Blaevens car as an example of why a H6 is a shit idea because its cheaper to do a turbo etc etc and that is rubbish. He did an all out conversion with lots of custom work that was not necessary. I personally like his car and i think the result was awesome. However all that work and money is not needed. Early EZ30D will bolt in, splice the looms and use the H6 ECU, some piping to match the dual coolant outlets on the motor to the single inlet on the radiator, and some piping for the air intake. Done. EZ30R add aftermarket ECU because of the CAN communication. Make life easier and have the two looms sent to someone like Al at AMauto to have them professionaly spliced together so you get a nice neat loom in the mail to plug the H6 straight into your Gen2.

It would be worth considering a few things like new rocker cover gaskets (very common EZ30D leak, not sure about EZ30R) and maybe a timing cover gasket, definitely sparks plugs (platinums and they'll last you 100,000km) simply because they will be easier with the motor out of the car. I just did the spark plugs and rocker cover gaskets in my H6 Gen2 and it was a farkin biatch of a job.

EDIT: Why not buy a stock H6 outback? Then you get a phat body kit and you can use the money you save on for a 6 speed conversion or something awesome like that. Seems a bit pointless doing it to a Gen3 when they came from the factory fitted with a H6. Yours will be a custom car (less resale value), and you will never recoup the cost of the conversion. Stock H6 outback = better resale, easier to sell etc.

yea i understand where you are coming from in terms of the 'cheaper' aspect of going with say an ej20t or a B4 engine for example. However im wanting something different, i drove a later model liberty (GEN4) with the h6 engine and was impressed with the responsiveness and it is a good base to work with. Also i have seen first hand and spoken with some shops that have performed twin turbo installs on the 3.0L..
Xon very nice, how does she go? yea lag isnt really why i was wanting to head with N/A, i personally didnt wanna do something that 99% of people converting engines go with as i think it takes some of the fun away from it because its a relatively speaking 'known' direction.
Venom, you are right about the price factor, if i wanted to i could very easily reach 13K on a 2.0L or 2.5L... i have got a pricing on an imported MY2000 outback with h6 engine, has the 4speed auto which im not interested in, its in good knick and they want 3.5K for the complete cut or 2.5K for just engine + wiring.
all work i will be completing myself so i will save on my labour costing.
I looked at getting the outback but i do love the gen3 shape (for whatever reason ). i understand about the resale value but at the end of the day i want it to be 'my' car and unique in its own ways.
would it be a better idea in terms of electrical side to get an aftermarket ECU??

If you're wanting to do something different then sure, the H6 will be that. If you do all the work yourself then I think you could get away with it pretty cheap. The problem I see with the H6 conversion is that once it's in, that's it. You can't really extract a significant amount of power from it cost effectively compared to just dropping a WRX/STi motor.

The v7 motor is great. Still a few issues to sort out with some sensors and what not, but it's great to drive. Nice and smooth, and power to boot when it's needed!

yea good point shiv...what exactly is different between the 'd' and the 'r' apart from obviously updated engine management?

oh ok, well yea i guess 30kw outta the box for a couple more g's is worth it i guess.. does anyone know someone wanting to sell an ez30r? cant seem to find any in 'salvageable' condition through my sources

If your car is a gen3, you'd be better off getting a BE/BH halfcut. More of the goodies that come with the cut will be compatible with your car that way.
If you do go with the gen2 cut, make sure it's from a GTB and that it's a manual, in which case the engine will be an EJ20R and be a much nicer engine than the other gen2 twin turbo engines.

I got everything I needed for the conversion supremely cheap so the price I paid won't really be relevant. For some perspective, a complete v7 STi cut (including 6 speed and brembos which I don't have) will cost you about $13k.