Set up my 78's 4180 for quick change springs a while ago. I had a wandering float level, the cause of which just made itself obvious yesterday, and the exhaust system is kinda screwed up by a previous owner but I was curious, all things being equal on a stock motor what spring do you think is prudent on an F250?

 

I tow with an 86 F250 4x4 460 C-6 with a 4160 Holley. I run a black secondary spring. On my wife's 88 Dodge D250 2wd, 360, 4sp with a 4175 Holley I run a purple. If you read the directions that can with the Quick Change Kit they tell you how to find the right size for your application.