Clark - The 1949 Flxible-Buicks were stylistic ground-breakers and, perhaps, the most advanced professional vehicles of their day.
According to the available Flxible production and delivery records, your car is an FB22-749 which means it was a Premier Ambulance. It was Flxible's body number 16311 and was delivered to the Webster Hose Company #3 in Ansonia, Conn in March of 1949. The vehicle's frame number was/is 15131153 and the motor number was/is 53327867. For your information, the 1949 Flxible Premier ambulance had a base factory drive-away (retail price) of $6,447 and in 1949 Flxible sold, built and delivered 403 Buick Roadmaster-based professional cars of which only 96 were ambulances (105 were funeral coaches, 190 were combination cars, 10 were service cars, 1 was a police patrol and 1 was unidentified).
The 2nd Quarter 2012 edition of The Professional Car (#144), featured a well-illustrated, in-depth, 15 page article documenting the 1949 Flxible-Buick professional vehicles. If interested, this issue should be readily available through Matt Taylor - the Professional Car Society's Store Keeper. I sincerely hope this information is of some use/interest to you and, should you have further questions, please do not hesitate to let us know. As you can see from the production statistics, there were not an awful lot of these ambulances built. As such, surviving examples are rare. We at the PCS would love to see photos of this car, will gladly be of whatever assistance we may be and and wish you well in the restoration. We would love to see this vehicle properly restored and preserved.