Looks good on the bike. Leave the '68 stock
. The best looking tail light on a Stepside is a Stepside tail light. For custom, just older smaller ones. Stepside beds have tail lights that are attached to the bed stanchions that stick out. It's ok, it's how it was meant to be.
How about a little better picture from Wheels Through Time? A Softail Knucklehead and a horizontal twin