I looked at the Airpower website, and they say new-reman engines are $29,000 each.
As for assembly, there are a lot of competent IA's who could do that, including the one that Herb and I used. However for what you want, I would turn to Owen Bell, or Don Nieser to have a project like that done. Both of these gentlemen have an extensive background with Skymasters, and either of them will do the job you need done.
Do you actually need new props, or can they be overhauled? Don owns the Prop Shop, in addition to his Skymaster business.
I have no idea what new props will cost, but I'm sure someone here will have more information.
As for the rest, Wow, tough choices. I would think that if you have been looking at the market for a while, and you found the "perfect" airplane here, then go for it.
Owen Bell is at
http://www.aviationenterprises.us/ and his email is
owen.bell@juno.com . His phone number is 615-865-1802.
Don Nieser is at
http://02337parts.com/ and his email is
nieser.02.337parts@juno.com . His phone number is 405-503-4686.