any one using a new rear end
You weren't clear, did you want to stay with the small 5x4 bolt circle, or switch to the larger 5x4.5?
If you're going to the 5x4.5, there are LOTS of options.
-Explorer 8.8, with limited slip and discs.
8.8 swap
-Pre '70 B body 8.75, no narrowing required, just use wheels with more backspace- it's only ~1" wider per side depending on year, spring perches are only 1" wider. SHOULD relocate the perches, but "some" people just spread the leaf springs a bit and bolt 'em in.
-People also use Jeep Wrangler and Liberty rears (8.25 Chrysler), a little wider than A body, but offset wheels do the trick again. 5x 4.5 bolt circle, limited slip, rear disc brakes.
-Ford 9". Early Mustang and Maverick units are a bolt-in, aftermarket is loaded with cheap aftermarket rears and parts.
-Narrow a truck Dana 60 and get appropriate axles. Same deal as the Ford 9, tons of aftermarket support; it can sometimes be cheaper to build a Dana than a 8.75.
what late model rear end are people using new challenger or charger ? I cant find any info on anyone doing it
Those are independent rears and would require re-engineering the entire back half of the car- frame, crossmembers, fuel tank, etc.