I AM TRYING TO FIND OUT WHAT REAR END I HAVE IN MY CAR.MY CAR IS A 56 CUSTOMLINE.ITS GONNA BREAK YOUR HEARTS TO SAY THIS BUT IT DOES NOT HAVE A Y BLOCK

THE PREVIOUS OWNER SWAPPED IT OUT FOR A 302 AND AN AUTO TRANS.I AM WANTING TO CHANGE THE GEARS IN THE REAR END BECAUSE OF THE CHANGE FROM MANUAL TO AUTO.ITS GEARED TO HIGH.ANY HELP WOULD BE APPRECIATED!!
TULARE,CA