I use Evercoat Lightweight filler, costs about 15 at the local carquest. I can't justify spending 50 plus when 90% of it ends up as dust on the floor.

68 Road Runner, 69 Belvedere, 71 Challenger Vert
340 barracuda, 01 Ram CTD, 95 Ram, 04 Ram, 85 Daytona turbo Z
66 GTO, 06 Magnum RT AWD. 07 Ram CTD, 07 Ram