Got Shell 93 Octane and now barely idles 1973 Dart 340

I tried a siphon pump but its goes about 3 feet and hits a restriction and no fuel. Possibly a screen where the filler tube mates with the tank? I changed the fuel filter and added the bottle of HEET. I will try it on Sat. morning. The old fuel filter no restriction and looked fairly new.

I have a new adapter and gasket for a square bore (Carter AFB) to Spread bore (Thermoquad stock original) intake. If I am unsuccessful then I will have my friend who owns the show that rebuilt the front end take a look.

I will probably pick up a cap rotor as well. I already have a set of NGK spark plugs to replace the Champions, because I don't know when they were done, but the 2 that I look at in each bank looked good with square electrodes and no fouling, no carbon).

Thanks for everyone replies.
Frustating. I have only put 250 miles on it since I bought it.
Eric