From the ever trustworthy Wikipedia:

81 - 89 Town Car weighed 4044.

90 - 97 Town Car weighed 4040.

I couldn't find weights for comparable Cadillacs but I imagine they were similar.

The land barge comment was not from CR but the article did emphasize that cars were getting bigger and heavier right when gas prices were rising sharply and there were concerns over the supply of gas. What's funny is that 4000 lbs is not out of line today considering how much a 300, Charger or Challenger weigh.

I remember a new car owner was suing either the EPA or the car manufacture sometime around 1990 because his estimated city mileage was way off. I think his car was a Town Car and he was getting around 7 MPG in the city even though the EPA had rated his car good for something like 15.