To check for frame squareness, measure from crossmember to crossmember in an X going from opposite corners. It's not easy to do on the ground, but certainly possible. You really only need to check in two or three places to tell.
Later
You can also use a long string and a tape measure, take the end of the string and tie to the front bumper then angle it down and around the leading edge of one of the front tires (the wheels need to be straight) and with the string centered on the tire go around the truck keeping the string in the center of each of the tires and tight.
Sounds kinda nuts but what you are doing is creating a datum line.
What you will end up with is a sring strecthed tightly around all four wheels and bisecting the wheel in the center.
Now if the truck has the same "track" or axle length and everything is undamaged and where it should be then the string will touch the front AND back of all four tires. Get where I'm going????
if the track is off, like the front axle is wider (IIRC commen)the the string will touch the front edge of the front tires and the rear edge of the back tires. Don't worry, you can still work with it thats why you have the tape measure. Measure from side to side and it should be EXACT. If not start looking for problems, assuming your wheels aren't bent, I'd check em again then start with rear spring hangers/bushings/center bolts ect.
Hope this helps! It took longer for me to type this than it would've to do it myself!
