Early A weight

Current new Mopar magazine list all the base weights in a chart. But all the 63-64 cars are about 100-150 lbs less than 65 and 66, then in 67 they started geting heaview untill 70 by a few lbs. Then in 71-73 they gainned a few more, lastly the 73-76 wore the largest.

The early 63-64 Base listed as 2850
add about 100-150 for a 65, Darts have a longer wheel base and com in a little more than a cuda, or valiant.

My 64 with a 273, 8 3/4 rear and a 727 trans weighed 2960 with the spare tire and all seats in it.

Have have gone tti headers probably a wash with the iron exh.
Added sway bars larger suspension added about 65 lbs
Aluminum water pump, and small starter save maybe 8-10lbs

Anyway that should ball park it for you. A typical 70 Dart weighs about 3250 base with a small block and a 904 and small rear end.