That should have the old style resisters with the contacts.
I put one together for my uncle about 15 years ago.
those don`t down shift. They just had the resisters and contacts (gas pedal)
and still used the forward and reverse solenoids just like the gas version only they were 36v.
As the electric motor rpm drops the current goes way up and it should power up a hill.
What is the problem with the cart?
slow or no power?
What have you done to the cart so far?
On a cart that old I would go after the relays and check the brushes inside the motor (rusted brush spring)?