Relocating the rear differential 1.25” towards the rear of the vehicle on a 72 Dart

All of ours make a loud clunking noise when shifting gears
especially 2 to 3.

We leave in a small town where everybody know us, so we
are only at full throttle at the Track.

We have Pro Trans reverse Valvebodies that shift hard, that
probably aggravates to clunking compared to a stock transmission.