Will reversed battery polarity hurt anything?

[pistonbroke]

My brother hooked up my 36 Dodge to neg. ground by accident once and I drove it for a year or so . The two things I remember were the amp gauge was backwards and the heater motor ran in revers making a horrid noise. The battery was under the floor(carpet and pad)so the obvious went undetected and the system maintained 7.5 volts so I as a young man of 27 was puzzled for quite some time. I drove it as a daily driver like this with no other issues .
Tim