I see all these posts on picking ratios and which is the strongest but what about making old rears fit new builds? Note: These questions and answers could vary depending on application. details and questions may need to be reworded to be understood. Where do you begin? Ads are full of rears for sale, when can they work for your application? I have an idea that welded brackets can be cut off and new ones added but how far does that go? We all know by now Dana 60 diffs are strong and preferred and Lots of used Dana 60 diffs with axles, usually from the front of a Ford truck are found for sale, are these modified for rear use by refitting axles and tubes? Is there such a thing as a rear too big or too heavy to use in a muscle car build? Those old GM 9.3" rears are supposed to be really strong, Ford 9" rears too, is it worth altering for a custom application or is it better just buying a new rear made to order from the factory? All these questions are assuming fair welding experience but no heavy equipment is owned or have access to, such as a mill or a lathe. Please expect I'll be commenting after many of you replies and Re-ask questions above, I find that in the majority of multi layered questions, only the first question is either read or answered (perhaps It's better to ask one at a time).