I am looking at an M37 to buy. Can an overdrive be added to this unit? Without one I understand the top speed is 45 mph. What gains in speed could I get if one is available to purchase?

Thanks in advance for the help!

I am buying a 1954 M37 that does not have a front winch.
The bumper is flat. Is it hard to convert to the winch style bumper? I am new to this so any help would be appreciated.