71 dart shooting flames from carb, wont start

my head gasket blew. so i decided to fix it myself. in the process, i dismantled the heads and cleaned them and the valves with a wire wheel, and oven cleaner. i cleaned the intake manifold and valve covers, with new gaskets. i replaced the valve stem seals too. i used all felpro gaskets and the copper spray sealant on the heads. i also replaced the water pump and starter, put on new thermostat and housing, and new battery. all napa brand parts (except battery from autozone). everything is back together.

i try to start my car, and it wont start. it just cranks and cranks, and sometimes shoots fire from the carb when i gas it. occasionally making a weird noise of air releasing (or pressure?).

now, my best guess is that i messed up the timing somewhere when pulling the distributor out during the process. i have the plugs installed into the cap in the correct order listed on intake manifold, and the dist rotor was pointing towards carb at 12 o'clock when viewed from driver seat. (#1 plug is also in that direction, but i think the wires may have been put in differently before rebuild)

so...

how exactly do i set "TDC" and get the timing set correctly? also, is there any other possibility that could be causing this? im pretty sure i installed everything correctly. could something i overlooked in the process be causing this?

please help, thanks for reading.