My Chevelle has a the original 10 bolt non posi rear end. I think it is an 8.2 rear and probably has 2.73 gears. I want to have a posi rear and somewhere in the 3:42 range gear...should I get a posi unit / gears for this rear, look for an 8.5 or pony up for a 12 bolt?

I remember years ago putting a 12 bolt together and having to get the right posi unit for 4:10 etc....do 10 bolt rears need to do the same thing?

For now it's going to have a .030 over 350, 10.5-1, 202 heads / cam etc....later down the road will be a BB of some sort....

if later down the road is going to be a b.b , i'd be going 12 bolt - mainly for the strengh of the case & tubes . but then their are guy's on here that run 10 bolt diffy's with hi hp , but also - their built for it .

if later down the road is going to be a b.b , i'd be going 12 bolt - mainly for the strengh of the case & tubes . but then their are guy's on here that run 10 bolt diffy's with hi hp , but also - their built for it .The other 71 chevelle I had years ago started off with a 350 / stock 10 bolt posi....not sure what the gears were, didnt know much back then. I tore it up, replaced it with another one and eventually tore it up as well. After that I went with a 12 bolt and didnt have any more problems....I'd rather not go 10 bolt, but it may be all I can find. If I can even find one of those.

A new Eaton Posi for the 10 bolt is $440 and a set of gears is $175. The installation kit is $92. Add that up and see if it makes sence to put that much into the 10 bolt. If you need axles they are $225 and bearings and studs are $55. So you have about $1000 in it without any labor. You could probably get a good 12 bolt off of ebay or from tlowe for about $1500.

as stated above...I personally don't think it makes sense to dump money into a 8.2 10 bolt...a 8.5 10 bolt would be a different story

if you are looking for an affordable way to just move up to a posi( if you can live with your current gears) I would recommend a lock-right locker. easy to install, doesn't require special tools so you can do it yourself, and it adds some strength to the 8.2. otherwise, ponying up to a 12 bolt/ 9inch/ etc would be a good investment.
like everything, all about cost and compromise.