Dude, the first thing you should learn from coming on here is that most dealers aren't well informed.  And they also have a vested interest in you buying parts and getting work done by them.  This isn't always to your advantage.  Nothing beats doing your own research.

It may be true what they say about the 2008 barrels not being suitable for boring.  So don't get them bored.  If you buy replacement barrels that are already the right size it's not a problem.  A quick search on U.S ebay will clearly show you that the V-Twin kits (one that I used) suit all sportsters from 2004 to 2010, see here:

http://shop.ebay.com/i.html?_kw=1200&_kw=sportster&_kw=883&_kw=conversion&_dmpt=Motorcycles_Parts_Accessories

Also buy from overseas you will save a shit load of money.  You don't need to go for the V-Twin kit, you can also buy the Harley kit, but buy it form the U.S as you will save lots.

Once you have the kit you want to find a good mechanic that will install it.  The dealers won't as you didn't buy the parts from them.  I had mine installed for $600 by K&M Motorcycles here in Adelaide, so use that as a guide.  You will also need a fuel tuner as your bike is fuel injected.  Get the engine work done first and then add the fuel tuner yourself.  The PCIII, Thundermax and TTS will all do the job.  The Harley tuner may also work but I don't know enough about it to say.  The PCIII from what I've heard can work but it requires dyno time which will cost you.  The ideal tuner would be either the TTS or the Thundermax.  The TTS is probably the best as it only tunes your factory ECU and retains the knock sensor.  I used the Thundermax which worked well but I did have to tune it manually for pinging.  But even that was quite easy to do in the end.

All up my sporty conversion cost around $2000 and that's with someone else doing the engine work. Half that cost was also the Thundermax.

About them saying that it will not go as good as a factory 1200 is crap.  They do, just ask anyone who's done it.  In my opinion, it's not worth spending more that say 2.5k on a conversion if you start to spend 3k +, then as they say you'd be better off selling your 883 and buying a 1200 as resale will be better.

 

Dude Kingchops is spot on.
M and M cycles quoted me about 900 i think for the HD screaming eagle kit wich basically makes it a stock 1200 with 883 gearing.
dealers are freaks for the most part they have no clue about anything aftermarket and will all bleat on about how harley does all this research so harley stuff is the only stuff you should put on a bike.
If you read the US forums as well as here you will quickly find there is much info and an array of parts both HD and NON HD that are great and go well on your bike.
My advice take your time I have had my Iron 883 for about 4 months still pricing and deciding on what to fix/change about the bike, after you ride it a while you will notice things like suspension in particular that needs fixing.
Read scotties posts on EFI too as if you do the pistons you will need a TTS or similar.
I spend hours reading forums and websites theres a lot of knowledgable fellows out there who have owned harleys for a long time why not benefit from others experience i say!!!
cheers
NR

the screaming eagle kit retails for $1199.95 us in the states..but most places will drop at least 10% plus shipping plus aussie dollar conversion which is good at the moment..
s/e supertuner /tts/pc111 all good pc 111 cheapest but needs a 1200 flash from a harley dealer about $60-00 bucks and can use a download map but dyno is better..
2008 on barrels cant be bored out (883-1200 is a 3x bore job!)
$3000-$4000 for a full 1200 conversion is about right
$1500-$2000 for a 883-1200 pistons and barrels only conversion..
1200 heads are buell heads with much bigger valves than a 883 and a totally different chamber and ports!!
the heads are the biggest difference and if you want to do cams latter the full 1200 kit is better if you just want a bit more torque and on a budget the pistons and barrels only is the way to go !!

please do . looking forward to see if any of these so called hd expert shops have to say if they read this post . it would probably be better for the shop if you upgraded to a 1200 . more money involved.
the hd shop up here in townsville are only too happy to fit a kit .

if you want a dynotune the best guy in melbourne is phil tainton racing in wantirna/knox he runs team suzuki but will dyno efi harleys....he is brilliant !!

yea-P.T.R. 98011287 dont think he will build the engine but best dyno guy i've ever used !!