I've painted aluminum with standard primer and overcoated it with an enamel without any problems. Cleanliness is the key. Any oil, grease and dirt should be cleaned off as best as possible.
I have a 30 year old Sensation lawnmower (which is the same as the Bobcat mower deck you have). It's probably one of the best I've ever used. My mower still has the original B&S engine on it and is still strong after 30 years but showing some signs of weakness. My father gave it to me because it didn't work and was going to send it to the dump so I took it off his hands knowing I had a good machine despite its problems. I put a new carb on the old B&S 4HP engine about 5 years ago and it works very well today. It cuts great and has been a excellent performer over the years even today. I will not trade it or junk it.
What engine did you get to fit the deck? I maybe in need of a new engine soon.
I stocked up on a bunch of parts for the one I have. After extensive searching on the web I was able to find the original grass catcher, several high lift and normal cut blades, original wheels, bolts and deflectors. I should be able to keep it going for another 30 years or more. I wouldn't trade this machine in for anything today. Nothing compares to it. It's built like a tank.