We would suspect that the clear or opaque plastic fuel filters that Chrysler used in the '60s and such would always have some fuel in them for us to see. By observation, NOT always the case, even on a non-vapor lock prone vehicle. Never did figure that one out and the old-line Chrysler service manager at the local dealership really had no answer for what we saw sometimes either, other than we knew it happened sometimes, even in not really hot weather.
I suspect that one orientation for having the "can" fuel filters is to also allow the extra space to serve as a pulse damper of sorts so that the needle and seat only see a smooth flow instead of one with pressure spikes/pulses from each stroke of the fuel pump.
If you're worried about fuel flow, then use the accepted method of securely hooking a length of fuel hose onto the pump outlet pipe and stick the other end into a stable and clean container and see how much flow you have during cranking (with the coil wire disconnected) for about 10 seconds or so. Then reconnect the original fuel line and put a pressure gauge inline to see what the running fuel pressure (with the coil wire reconnected) might be at idle (usually somewhere about 5-6psi). If the container was clean enough, you can recycle the fuel from the flow test--otherwise it might make good lawn mower fuel. If the flow and pressure are in spec, no problems even if the fuel filter might not even be 1/4 "full" by observation.
Typically, Chrysler products were not nearly as prone to vapor lock issues as were many GM and some Ford vehicles. Chrysler's fuel line routings, by observation, usually did not get that close to heat producing parts of the car before they got to the fuel pump.
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