What transmission do I have?

I recently purchased a 1994 33' Holiday Rambler. I know that it has a FI 460 V8 gasoline engine, that it has a 5.13 rear axle, and that it's built on a Ford F Super Duty chassis (though I thought it had a F53 chassis, very mysterious). Now I'm wondering who made the automatic transmission. From what I understand after reading Fords inadequate owners manual is that it's a 3 speed + OD and that Ford recommend using Mercron automatic transmission fluid. The reason I'm asking is that I'm a believer in synthetic lubricating fluids and preventive maintenance. That being the case I'd like to change out the AT fluid for a high quality synthetic.
Steve