1931 Lasalle heater installation

[George]

We are in the process of installing an original accessory Cadillac hot water heater in a 31 Lasalle convertible coupe. It did not have a heater in it originally and the holes in the firewall do not match up with the tubes from the heater. We are planning on punching holes in for the tubing but are uncertain exactly how high up under the dash the heater would be, if in fact it is behind the dash. Mounted to high would cover the louvers and the Cadillac heater tag on the front but mounting to low would interfere with the passengers leg room. Basically it almost looks to be to tight of a fit but we believe this is the only hot water heater that was offered by Cadillac and was used in all their models. Any help in the form of descriptive information or pictures of an existing installation would be of great help...Thank you!!...George, email gchrin@aol.com