I don't remember exactly how much I bought. I ended up having to purchase a bit more. I also did use it on the entire care because I found it after I had already complete the engine harness. I also order much more than I would use on the car for other projects, I tend to be a bit addicted to stuff like this an heat-shrink tubing.
I think I used 10' of the 1" for the main harness in the tunnel. Very little of medium sizes and quite a bit of the smaller sizes for long runs of just a pair of wires. I ended up ordering at least one 10' of each size from 1" on down and re-ordered more of the 1/8" and 1/4".
I know that doesn't tell you exactly how much to order and that's going to vary from build to build. But hopefully that gives you a better idea.