[blucar]

An easy way to tell if the Columbia is in fact a '39 is to look at the radius bars.. do they bolt to the back of the backing plates like all '37-39 and later. If they are attached to the axle housing it is a '35-36 or a combination thereof.. I have seen Columbia's that were '36 on the stock side and cut down '42-48 on the Columbia side.
As previously suggested pull the shift can and check the unit out.
If everything checks out OK, then either fish or cut bate... Pull green money out of your pocket, $500/600 from one pocket, keeping some reserve funds in another pocket. Anything around a $1,000. would be a good deal.
The nice thing about a Columbia is that they are a bolt in application where-as the Mitchell requires a lot of modification to the chassis..
The Columbia gives you six forward gears, and a quick passing gear which the aux transmissions do not.
I replaced the '36 Columbia in my car with a '42-48 Columbia with vacuum electric controls... It has worked great for over fifty years.