Rear Axle, Which Method for Bolt Pattern Conversion...

To be honest I would prefer having a 318 over the 225 /6 (But can't be choosy, seeing a 4-door 70-72 Valiant perioud is tough, let alone a $2,500 in good daily drive condition...) but I've no idea how much that would cost or the work involved, especially a carburetted version