As I remember my street Challenger (SB 4 speed) was right around 3600 w/o driver. The factory bumpers weigh nothing. Hood helps. The cage is probably at least 120#. A Mega block weighs around 75# more than a 440 block. You can always work on it. My 64 Belvedere comes in at 3130 w/o driver,full interior (-back seat), mega block, 2 batteries, Dana, all steel exc hood.
Doug