Agree.
First, if they are still separated, make sure the body is fully supported and braced. You don't want all that nice body work (and your money!) going down the tubes because the body flexed and kinked.
Try to put as many systems on the frame as possible before the body goes on. It's just easier to work on.
That means pretty much start at the bottom. If you don't want to support the frame on secure stands, then support it on the tires, axles and suspension.
Run your brake lines, fuel lines, and maybe even the pertinent electrical along the frame to the rear. Fuel tanks and any wiring for electric pumps included.
You can't do 100% of it because some things, such as rear lights, fuel selector valve (if dual tanks), master cylinder and such are mounted to the body. But you get the idear.
Engine and transmission next. Forget the driveshafts and trackbar until you have the body back on, but for now working on the majority of the drivetrain is easier with access like this. With luck you'll never have the body off again, so take advantage.
When you've done all that and figure you're close enough, THEN put the body back on the frame with new body mount insulators. Whether stock, stock-height polyurethane, or 1" body lift, new is good.
And by now you'll have discovered just how much of "complete" your parts acquisition really was. Still have yet to know of a single person that bought a "Bronco-in-a-Box" setup that did not find a ton missing that had to be sourced later.
But you could be the first!
Good luck. And welcome to classicbroncos!
You can upload images (which we love by the way. Gotta have pics!) into your "garage" or "gallery" functions, or if you're a computer/internet kind of person you may have an image hosting site you already use and can link the photos to here. Or you can pay your 12 bucks a year to become a contributor and then upload them directly from your device to your discussion. Not everyone is ready to jump in and pay a website right away, but it's a good way to keep this place partying!
Have fun.
Paul