Andrew: Read Dennis Frisk's post carefully and ignore mine; I was in error,
The 147 is a narrow frame and uses a different mule drive. The next step is identifying the model of the attachments on the 147 and figuring out which mule drives to use and how to set it up. Unless someone is able to vouch for mating the particular attachments available with the 147 with the 149 and is able to tell you how the mule drive was set up to do it, I would stay away. It sounds to me as if you might be buying yourself a lot of trouble.
As far as the engines go, you might be able to use the two engines to make one, but you need to assess their mechanical condition. The easiest way to do that is to pull the head off of each, check the smoothness of the bore, the valve lift, and general condition.
Matt: I talked with Roy Najecki last night, he told me that he too wound up looking for used aluminum-bodied spindles per your advice. Since the dealer can no longer source the ST745 "water pump bearings" from Cub Cadet, but is pointed toward the aluminum-bodied unit as a substitute / replacement, I wound up buying the new-style assembly with the old-style replaceable bearings.
Even though they set me back a pretty penny (a little less than what Dennis spent), I felt like I would be going backwards by buying new steel cups for a semi-good "water pump" bearing which, when it fails in a few years, would land me right back where I am now. If I were handy with a welder and had access to machine tools, I might fool around with trying to repair the cups because that is where the biggest part of the problem lies.
Every other deck I've repaired cost me $200 tops for all new spindles, belts, and blades; the Cub Cadet parts START at almost $200 per spindle.
They had better last a good, long time . . .