Please Use Search Function, this has been answered countless times. This thread is from 5 days ago and is from half way down this page, it will answer your question on a lift for 31's, I am assuming you have a '97 by your screen name. It even has links to parts you need on the summit website.
And here is how high it will sit on 31's. Approximately 22 inches to bottom of rocker panel.
'98 Ranger XLT 4.0 4x4 auto, AVM's, 31x10.50's. DD
'03 Mineral Grey Cobra- turbo 5.3 lsx project, TH400, 8.8
'92 Mustang GT- full bolt ons, 4.10s
'70 Chevelle Malibu- 454/muncie, slow frame off resto in progess