Not to bash on the OP or anyone else in this thread but I've never understood why people have so much trouble with the defrost hoses.
First, you want a material that's flexible and not heavy. I can't tell for sure but the pics look like a heavy rubber type hose - not ideal.
Second, don't bother with adapters. There's not enough room for them and they cause more trouble than their worth.
Third, prepare to get creative with how to attach the hoses to the heater box as well as the defrost vents.
Here's what I did on my '71 Dart 13 years ago. Look online for some hoses with the correct ID to go over the heater box fittings without adapters. As other posts in this thread show they are different diameters. I found mine on ebay, generic hose ducting. Buy some length of that hose. Make sure the hose is flexible or can be formed from using a heat gun. I attached those hoses to my heater box with big zip ties, 1 on each, pulled tight with a pair of pliers. The factory clips for attaching the hose are nice if they're in good shape. You could also use duct tape (black color) if done correctly with a good brand of tape. Another option is going to the hardware store and looking and different types of radiator hose clamps. If you go that route be gentle and don't make them too tight. As far as connecting the hose to the defrost vents on the passenger side vent the hose was able to just barely fit inside of the vent fitting. I think I had to make a slit in the hose to allow it to collapse a little. I attached it there with good quality duct tape. On the drivers side the hose just barely fit over the vent fitting and I attached that with duct tape as well.
I've had no problems with this setup and has held up fine after all these years.
