I love old car heaters only slightly less than modern car heaters.*
The thing I love the most is the way that every car since about 1950 has been built fully around the heater, so that you have to start by removing the tow bar, tail lights, rear seats, carpet, headlining, garage door, kitchen sink etc etc etc before you can get to any part of the heating system. Any attempt to short cut this process will be met with several hours of swearing and cut knuckles, before you decide that removing the tow bar etc will be the way to go, and start over. When you finally do get to the heater, you'll have no way of draining the heater matrix before you remove the pipes, so you get the beaut rusty water tsunami upon disconnection. (Bet you wish you'd lifted the carpet now, don't you). Installation is the reverse of the above process, just with more swearing.
Don't get me started on siezed operating cables and flaps...
*Hagar has recently fitted a custom heater setup to his project car. This involved cannibilising (sp) several modern cars for parts. The scars are not yet healed, and the heater valve is still not right, despite being on version 4.