series III heater in a series IIA?

[farmer]

I have a 1970 series IIA 88 that had the old smiths box heater under the hood and i want to replace it with a unit out of a series III. I have both units out and in front of me and the newer smiths unit from the series III is thicker the hole in the bulkhead needs to be 1/4 inch bigger on both sides, this is no problem. the problem is the newer unit is made to sit higher and the outlet must come through the bulkhead in a different place. has anyone replaced a newer smiths in place of the older unit? any advice would be greatly appreciated.

[farmer]

ok i have done a little research. I have an early transitional smiths heater with the padded distribution box that runs just under the dash.