high lift springs

So I have been helping a friend convert to a high lift.  I have installed and worked on hundreds of doors but never a high lift.  My question is about springs.  I tried regular springs and obviously they did not work.  I have done some calculations and it looks like I need 2 .289x74.5in. springs.  Does that sound right?  I mean the length because I just dont want to order springs and pay all that money and not have them right.  Thanks in advance.

I would recommend using a local garage door company & ordering through them. Most have (or have access to a supplier that has) a computer program that will calculate the correct springs if you give them the door size, door weight and how much lift clearance the door has. If you go with a larger diameter spring (like a 3-1/2" ID) the springs will be shorter.

Thanks.  I have been working on Garage doors for 6 years now, just never done a high lift conversion.  I use SSC to do all my calculations im just trying to see if that sounds right before i spend the money.

Are you using their spring software app? It works pretty well. I would recommend calling them so you get it right. They'll ask you all the right questions (door size, weight, cable drum size, amount of lift, etc.) and figure out the correct springs.

Yep, I love the app, works great.  Just going over what I need for this since I know the regular old springs I put on wont work and 70+ inch springs are a little overkill.  Looks like an ID of 3.5 brings the spring down to almost half the length so thats a great thing.  Now to order them.  Thanks again.