FYI...you might want to shy away from the 62" wide Australian Borg-Warner disc/posi found in the 88-89 Camaro IROC-Z's. Aside from being quite pricey, the availablilty of axle seals is going to be an issue. I couldn't find any supplier so I have a 3.08 dust collector.
Finding a Camaro 3.73 is tough.....however, the above mentioned Ford 8.8 at just a tad short of 60", would be a viable option. I'm running one (it's a solid axle) out of a 94 Explorer ($100.)....3.73 posi/drum in my GM 355 powered 40 Sedan and with the 31 spline axles and I venture to say it's plenty tough to use behind a 350. The posi clutch rebuild packs are about $125.00 and I've yet to find one that has any gear or bearing damage.
As for discs in the rear of a pickup.....with an adjustable proportioning valve, but without a good ABS system, you're going to be dealing with rear wheel lockup......especially if you're running a boosted brake system. Dics up front with drums in the rear are much more predictable.
Good luck with the yards accurately telling you what ratio tranny or diff you're purchasing. Easiest way is to jack up one wheel, spin the hub TEN revolutions while counting the pinion revolutions.....multiply pinion revs X 2 and divide by 10. This will give you the first TWO numbers of the R&P ratio. Ezample: rotate a wheel/hub 10 times.....counting 17 revolutions of the pinion yoke....multiple by 2 = 34....divide by 10 and you have a 3.4X R&P ratio. You won't have to guess at the second number like you would if you only spun the wheel once.
Also...if you use an 8.8 be sure to get the u-bolts and bottom plates. The axle tubes are a larger diameter then the standard 3" tubes. If you use a Camaro diff....be sure to get the rear sway bar as you can flip the bar from the bottom of the diff to the top, using the stock hardware and drill 2 holes in the frame and use all the Camaro hardware to attach the control links in front of the diff.
