So i think I have a plan. I have exhausted a number of suppliers in terms of SS pipe plus its too hard bend into shape and to bead in situ. To top it off the EZbeaders don't come in the correct size to bead it anyway as others have pointed out and the material is too hard to bead easily. So here is my thought process:
1. Copper has been used in auto cooling systems with great reliability for many years. I know the materials will be suitable and reliable.
2. Copper has been used with success by fellow X owners as replacement cooling tubes in a variety of configurations.
3. I can bead it in situ without the need to remove the tunnel (see tool below). I plan on soldering the front sections and beading the rear coming out of the tunnel
4. Copper will outlast me. I don't have a care about making the underneath of the car pristine for the next unfortunate sole who wants to attempt to maintain this car after I'm dust!
5. Copper is cheaper than SS and available in 1 3/8" OD so it will fit nicely into the tunnel.
6. In terms of removing the tunnel, cutting it, redesigning it etc. I have no interest in opening that Pandora's box. Some here have done fantastic work in this areas but they have the car on a rotisserie, they have the space, a lift and the welding capability. I do not. But I am good at solving problems and seeing it through to a job well done. Trust me the job wont look half arsed and it will function well.
That addresses the coolant tubes
Now as far as the heater pipes. Internally I can replace the pipe that runs inside the shifting tunnel in the cabin as its accessible. I've already rebuilt the heater box with a new valve, replacement pipe from MWB and had the core boiled out and pressure tested. This leaves the pipe that's in the tunnel. My plan is to retire it in place and bypass it external to the Tunnel. See crude drawing below.
Check out this beading tool. Looks promising. Ive ordered one and plan to use it to bead the copper tubes.
https://www.facebook.com/JobberDo/