Stay away from running a lunchbox locker in the rear of a daily driver (personal preference). If you decide to lock it up, remember that unless you know how to do diff work your self, you will have to pay someone to do it for you, which will cost money. A Detroit runs around $440 x .0775 (california tax)=$475 roughly. Then you have to pay someone else to drop it into your diff. So give or take roughly $50-100. Unless you can find a Detroit for under $400, then your hosed. You can probably find a used one for $300-350. Personal preference, I'd get a set of 4.7 gears, and do the grinding myself. You won't need driveline work done. You won't need a new crossmember. You won't have to go to any specialty shop. The instructions are one the web, and most anyone with any sort of access to commonly found tools can do it.
