I have the heater manifold but no top. If I had a picture of the top I could make one.The wife wants a heater???
If we had a photo of your heater manifold It would help since many different after market units were produced.
A few pics of ours, on our 24 Tudor.
Ken---------an alternative to a manifold heater is a golfcart catalytic heater which can be used inside the car. Its fired by a small (16 oz.) propane screw-in cly and no venting is neccessary. Damn thing really puts out some heat--just need to find a place to mount it so you don`t scorch anything. Mine was designed to fit in a golfcart cup holder and it will run for 7 hours. Check it out---might work for you. Paul
Note that the catalytic heater will send out CO2 and H2O.
The first was in many years not a problem ;-) but the second could be in particular if you begin to start it in advance in weather like on the picture. The water ('cause thats what H2O is) will be dew on the inside of your windows and humidity in all clothing inside the car.
When you drive "natural" ventilation will take care of most of the water.