advice please: replacing fuel system parts...

...do i replace everything? here's the situation: new motor but backfires throughout the rpm range. isolated it to the fuel delivery system because it runs fine after i clear the jets but of course starts to backfire again after contamination. initially had problems isolating backfiring due to leaking fuel line (under the car from the tunnel) and leaking exhaust (SSI to pass side muffler). i fixed both of these problems.
i have a good used tank getting boiled/sealed and plan to replace this weekend. the carbs were rebuilt and installed at the same time as the motor. i did not replace the fuel filter when the motor was installed - dumb. the car probably sat long enough in between projects (cv rebuild and motor swap) for the fuel to varnish. however my 2.2 did the same thing on its' last voyage - didn't know better then.
so my questions: do i need to replace a perfectly functioning bosch fuel pump for fear of particles? the see through $2.50 fuel filter should be sufficient, yeah? recommendations to install 2?
any other advice appreciated. thanks!