If you are talking about the Heater Channel, They are not difficult to replace if you have some metal working skills, a welder and various other tools. If you order the deluxe channels they come with the inner heater tube, important if you will be driving the car year round. They are a complete unit and will go from the front firewall to the rear wheel well.
1968 is the first year of IRS (look and see if the rear axle has a boot at each end of it) Only the Auto cars were IRS in 68. After that STD and Auto cars were available in IRS.
