You want to check up travel 3 ways ,support frame a good ways off floor and pull both springs, shocks(only top mounts) and front tires,now jack front axle up level into frame as high as it will go or until it comes into contact with something, now measure from top of frame to top of collapsed shock. Now drop axle onto floor,leaving one side on floor and jacking other side up until it hits something or stops and measure from top of frame to top of collasped shock now drop that side down and do other side. Next you can put on a tire one side at a time to see if it comes into contact sooner so you know what to cut out for full compression. You also have to remember what full compression of spring is( thickness of coil wire times number of coils)so that is a limiting factor also for up travel. So that tells where to mount upper shock mounts ,then where to put bump stops remembering that a bronco on the way down will smash them farther than a jack will.I mount my shocks so there is 1/4 inch margin. lifting an axle level and one side at a time will show differant lenghts. And while you are doing this spin driveshaft to check for u-joint bind and drop axle level to also check for bind in case you need limit strap. It is hard to check droop because a coil will strech further when off road than setting in the garage. A good way to check your results is to put a small plastic tie around shock shaft and see where it stops after a day of wheeling,or watch dust line on shaft. As for having no body or engine in frame I think I would tack towers in place to be checked later.Even after coil settles the axle can still only go so far up,and coil bind never gets any shorter, so shock mounts are always good.Now is a good time to see what is limiting travel,trac rod, c-bushings,radius arm mount at frame, bottom shock mounts.