I can't remember what pre filter to use with an external pump.
I guess something cheap but will work.
Needing 3/8" inlets as it's a 255 pump and I'll use regular hoses on the upstream side of the pump.
Someone said at one time the parts stores may carry them.

Also do we really need to run a post filter or after the pump?

 

For a pre-filter, I'm using the Earl's 230206ERL. It's $35 with AN -6 fittings. I think they make a hose barb version if you don't want to spend AN money. Check Summit.
Andy1

 

Depends on the pump.

for a rotary vane a 100 micron works. Most gerotors say 40 micron.

 

I was told to use napa 3482

 

You DO need to run a post-pump filter to protect the injectors, which are more sensitive than the pump to fuel crud. A 10-micron unit will do it. Mounting the filters immediately pre- and post-pump is the easiest to do from a servicing and installation viewpoint.

 

What filter size...will depend on the injectors used, but for pre-pump 40-100micron will be fine when correctly sized.

Some injectors are fussy as ****, others not so. ID are very fussy, Siemens less so. If you can get 10 microns or lower post pump, then that should cover most injectors.

And for any pre-filter, ensure it has adequate flow ability given you're relying on gravity. EFI pumps do not suck, nor do they like to try and suck so using a small filter like the Earls one above is not a good idea even if some get away with it.
Bigger is most definitely better here given the volumes of fuel that will pass through it