Chances are he's referring to the post above his which is not the OP. The OP was reviewing a product and someone hijacked it with a for sale ad.
The short answer is yes it will fit providing all mounting plates, screws and instructions are included. They are a generic fit however I think when ordered for a D22 you get D22 instructions and when you order for a D40 you get D40 instructions. The unit is the same but the way it mounts is different.
Personally I wouldn't pay $300 for a second hand one no matter how old it is, considering that you may still need to buy the CB radio surround ($25 3 years ago) and because it's a bit hit and miss installing one in a D40 with the instructions, without instructions you may as well get a seeing eye dog. It is easy to install but you need to have a fair idea where things are in the roof if you don't want extra holes in the roof lining. I'd rather pay $80 more and get a warranty but each to their own (...and I don't care if I offend when giving an opinion).