It certainly wouldn't hurt to have a frame strap on both sides.
Looks like that passenger car "
battery ground" attached to the front of the engine block.
Illustration (note arrow: 2.341 Ground Strap)
MPC shows in 1955-56, the passenger car used a "
engine ground". no other years shown.
Grp# 2.348 Note: MPC refers to the "
battery ground" as a "
Strap - Cable"
Grp# 2.341 and the"
engine ground" as a "
Strap"
Grp# 2.348 
