1971 C10 Rear End Swap?

Recently purchased a '71 C10 longbox. I am about to pull the 350/TH350 motor & trans and embark on a nice mild rebuild (more than stock, but not too crazy).  I checked the rear today, researched, and appears that I have a 12-bolt non-posi GM truck rear end with what appears to be 2.56 or possibly 2.73 gear (one turn of the rear tire - one side up - provided approx. 1.25 turns or a little more on the drive shaft).  I would like to get 3.55/3.73 posi rear in by next spring.  Are there any other GM candidates for a full rear end swap that will bolt directly in without mods, and available at the salvage yards for a reasonable price? Maybe something from a later model truck or suburban?  What would you do?  I am on a budget.  Any help or suggestions appreciated. Don't need anything bulletproof - engine will probably be a solid 300hp or so.  Thanks, roomor  

does the rear have leaf-springs or coil-springs  

This is a coil spring suspension in the rear.  

You could have it rebuilt for less than $1,000.  JEG's and Summit both sell rebuild kits and you could reuse the stock axles as long as the area where the bearings ride are free of any marring or defects and the splines are in good shape.  With only 300 hp the rear end will be plenty strong.  A buddy of mine has a '70 with a 500 hp supercharged 400 and it takes every bit of it... And he doesn't baby it either!  I have about $1,200 into mine, and that includes labor to assemble it.  I put in new bearings and seals all the way around, Richmond gears, Auburn limited slip, and Moser forged axles.  For the coil spring rear end set-up, if you want to get a late model rear end from a wrecking yard and then get a set of replacement saddles(the flat brackets welded to the tubes that the trailing arms bolt to).  It seems like Early Classic Enterprises carries those.  This might be a more inexpensive way to go, but if you need to add any internal parts(change of gear ratio, posi unit, etc.) then you might as well stick with the stock unit and rebuild.  

72 is the latest axle that is a bolt in, with no mods.  Finding a 3.73 shouldn't bee too difficult.  A lot of 6-cylinder trucks had 4.11's.  If you are lucky, you can stumble across a posi pumkin, while you are at it.  
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