The Jensen transformer is shown mounted to the chassis floor via a mounting kit from Jensen.
However, Jensen recommends that the transformer be isolated from the chassis if possible.
You could simply wrap the transformer with electrical tape, and then use double-sided sticky tape on the chassis floor and set the transformer next to the 1/4" input jack. There should be just enough room.
Also note that an optional Corcom EMI filter is shown on the upper left hand side of the picture above.
The stock Kenwood AC EMI filter will look a little different.