On a 1985 ford 302 what can cause turbulence in the fuel filter?

Engine has mechanical fuel pump and carburetor
Has a glass filter before the carburetor it gets lots of bubbles and turbulence in the filter also if you park on a hill with engine up the gas runs back out of the filter
The engine is in a 1986 Isuzu pickup it has 3 lines from tank 1 big 2 small I have only the big one connected to mechanical fuel pump

That pump should have a return line on it unless its the wrong pump. That serves a purpose. Its to keep your fuel cooler so it doesn't tend to self ignite and also has a neat cooling effect on the carb. Anyway, your problem is probably the pump, but regardless, somewhere you have a leak.edit* don't know who the jackass was, but don't believe me, verify for yourself. Ford started using a recirculating fuel system back in the 70's on the 302. This was to combat detonation and to help pull more power from the engines, especially since the engines were designed to run hotter than previous v8 engines. Gotta remember the intake now had exhaust gas recirc built into it! The heads were restricted by the air injection humps, etc. Engine was designed to be used with 4 catalytic converters. This is a ton of extra heat!
not sure exactly when the changes were made, because it wasn't all changed at once.
realize even all efi systems use a recirc fuel system as well. Do you think auto makers just decided to throw in unneeded systems for no reason other than to complicate things?