I'd find someone selling a "decent" stock steel tub. When I say decent, I mean one with good rear 1/4's, floor, strikers and wheel wells. Also, a good cowl, door posts, upper floor behind the seats and front core support. The common (basically next to impossible to find one without this work needed) problem areas are inner fenders, front floors, kick panels rockers and inner rockers. They can be replaced at a fairly quick pace, and aren't too much $$$ from the vendors. Tubs come up for sale from time to time, but usually don't last long. I've seen them for sale from $1k all the way up to $5k+.
Buying all the available sheetmetal for these vehicles and putting them together is a pretty extensive undertaking especially if this is your first bronco resto. The aftermarket sheetmetal is ok at best at times and can require alot of trimming and beating to get square. Not that it can't be done, but if you're looking to get it back on the road again anytime soon I'd find a "decent" tub, fab up a rotisserie and get it media blasted. That way you can enjoy your patched up ride while you get the other tub in top shape. It will also be a hell of a lot cheaper.
Oh yeah, I do not know of a set of instructions or even a step by step using every aftermarket part to put a tub together.