I have 3" pipes and mufflers that finish in front of the rear axle, they both weigh around 50#.
Isn't your new car lighter than the old one?.
Mick

69 Dart GTS 440 mopar .590 cam, Edelbrock heads, 3200#
best et 6.45, 106.78, 10.14, 132.88 mph, 1.47 60ft
best 60ft 1.36