H1B not stamped, changing client within 50 miles

My h1b was approved 4 months back and havent went for stamping yet. Now what if I change the client and location of proposed project in US? I know an amendment and once approval notice received I need to go for stamping. But if the proposed location is within 50 miles of actual approved location what is the process? I heard amendment not needed. But while going for stamping which client details should I provide? The new one or the approved one?
Experts your comments please? Please note the approved client is no more our client and I am still at offshore.