Reply to "My new 71 pantera, need help"

To expand a little on what Bayani said, your pre-L Pantera has a welded-in standpipe inside the fuel tank to deliver fuel to the pump. Condensation INSIDE the tank over 10 yrs of inactivity can and has rusted through the 22" long steel standpipe. So if the fuel level inside the tank happens to be below the rust hole, no fuel will be pulled up by and external fuel pump. You can verify this by filling the tank to the top. If it then starts, you have the dreaded rust hole and resulting limited fuel capacity as the pump won't pick up the full 21+ gallons in the tank.
If it still won't start, you may have a clogged fuel pipe filter-sock. This is a nylon filter on the end of the fuel standpipe, that is well known to varnish up, preventing some or all fuel flow. To fix this, pull the left rear quarter window out of the body and the engine cover panels. Then remove the air vent fitting and/or the fuel gauge sender out thru the window opening. CAREFULLY peer in the tank with a light and if the dark brown sock is still on the end of the standpipe, either blow it off with an air compressor or reach in with a long rod and tear it off.
Be very careful using a compressor here; it's possible to blow up to a gallon of fuel out the fill-pipe or any other openings in the tank, and it's also possible to rupture the tank seams if the fill cap is still in place. Tanks are difficult and expensive to replace. Fires from spilled fuel are worse.
The only other known fixes are-
A- replace the tank. The stock standpipe is unrepairable and the sock filter is unserviceable.
-B- replace the fuel gauge sender with a late model one that has a fuel-out line built in. This is a bolt-in factory upgrade from mid-'73 on. No need to pull the engine/trans/fuel tank. Plug the OEM banjo fitting welded to the internal fuel-out pipe. In the unlikely event that you upgrade to EFI in the future, the leaky internal standpipe can be used as the mandatory EFI fuel return line.