How difficult is it to install a new front to rear braker line in a 68 coupe. Any tips or tricks are appreciated.:)

It's not that hard to install the front to rear brake line. If you are talking about the one that runs down the side of the frame. You just have to disconnect it in the front at the distribution block mounted on the frame below the master cylinder and at the rear at the cross member under the back seat area. The 70 has a valve back there, but I believe the 68 did not. It should have a couple of clips also holding it to the frame. You brake system will need to be bleed once the line has been replaced. I'm assuming it is simular to the 70 since they use the same frame. How hard it is to do will depend on how hard it is to get the fittings off since you have a 40 year old car. Things never go how you think they are going to go working on cars. Good luck
Ray