No, I wish it was that easy. The cases have to be split so they can be bored to accept the 1250 cylinders larger diameter spigots. It ends up being close to a $5000 job including the 1250 kit for maybe a six horsepower gain. I looked at doing it and gave it a pass. You can get as large a power gain from intake, exhaust (if you choose the exhaust system carefully, not all work that well) and re-mapping the ECM.
There is this loon ball in my town with a stock displacement D that has had the heads ported, some sort of aftermarket cam, drilled out air box lid, K&N and Supertrapp slip ons and a dyno re-map. That thing is F-ing fast, but it gets 28 mpg if that.
you can buy a new 1250 from hd for about 6k almost cheaper than modifying the 1130 and you would have a spare motor.. if you are going to the expense of pulling a 1130 motor apart a 1450 is probably the best bang for the buck if you get the welded stroker instead of the billet crank..