Are you using the 883 heads on the 1200 conversion? If that's the case definitely stay with stock cams until some head work can be done. I would recommend buying a set of buell thunderstorm heads or late model 1200 heads as these can be purchased for $600-$800 new and provide the best bang for the buck.
The 883 heads are very restrictive and I would advise you to watch e-bay for a set or 1200 heads.
The 1200 kits for a 883/1200 have different pistons and will not work with 1200 heads latter on. I did my 2003 883, and I watched many who did the 883/1200 and it simple does not have the same power as a 1200 stock engine has, cam will be a complete waist of money and the heads are the problem.
Did you order the 1200 kit for 883 heads? Given that you live in Canada and winter is already here I would wait and save a little money to buy some better heads you have all winter to complete the project. I don't know what it would cost to ship from US to Canada but St Paul hd sells thunderstorm heads on ebay for about $600 usd I bought a set from them about a year ago. Worth every penny.
The main problem with a big bore kit for a 883 is that, since the combustion chambers on the 883 heads are smaller than the stock 1200 heads, the pistons in the big bore kit have dished (recessed) tops to maintain the original compression ratio. So if you later go to 1200 heads you will still have the dished pistons and your compression ratio will be lowered (if you get my drift here). Stock 1200 pistons are not dished. This is the downside to 833/1200 big bore kits. I suppose you could have the 883 heads ported and big valves put in but you would still be limited in the size of the combustion chambers to deal with the dished pistons. It might even be possible to have the 883 combustion chambers opened when you have the port job done but I really don't know if there is enough meat in the 883 heads to do that. You'd have to ask the guy doing the port job if this is possible.
If wuz handing out advice here I'd recommend cancelling the big bore kit unless you will be happy with the limitations that kit will put on further mods. Otherwise if you ever want to add the better Buell Thunderstorm or 1200 heads you will have to change the pistons to flat tops at the same time. I hope this makes sense.
It's only about $75 to machine out 883 combustion chambers to use proper pistons. Use the S.E. .575 Cam for a screaming machine with no headwork.
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For $4.00 you can still get the old template that was with the original SE 1200 big bore kit. You have to open the chambers up till the template matches the chamber. Then you can run stock 1200 pistons( about $140 here for piston, rings, etc.) & have the comp. set at 9.7:1 which is ideal for the sporty. Through in a thinner head gskt. if more comp is what your after. The smaller valves & ports of the 883 heads with the way opening up the chambers unshrouds the valves keeps port velocity up. If you want to turn the motor more than 5500 rpms, then the larger valves are the way to go. The stock gearing on the 883 is a little lower & the higher port velocity makes for a real good stop light to stop light little stomper. I have a 99 conversion that makes 62hp & 82ft/lbs with a cv carb on an eddy curent dyno. The dyno jet 150 shows a little higher numbers but I trust the Factory Pro dyno more. My wifes 01 883 is getting the more labor intensive big bore kit along with a 5 angle valve job & a little cleaning up of the ports & back cutting the valves 30 degrees this winter.