A good rule of thumb is .001" of bearing clearance for each inch of crank journal. So .0025"-.0030" on the mains and .0020"-.0022" on the rods. If the engine is going to be run warm quite often, you can go tighter, or just run a HV pump and do a little oil system massaging (smoothing, enlarging passages).
I don't really recommend doing it (though I have in a pinch), but I've used worn out scotch brite (green) on the face of the bearings to gain clearance. Keep clean solvent running on it while you run the SB across the bearing. I hold the bearing half in one hand and scotch brite on my thumb of the other. I cover half the bearing and count the number of strokes. Flip the bearing, do the other half. Then I flip it again and lightly go across the whole bearing face. You won't gain much, but if you're close it will work. And if you go to copper, you've gone too far. Kind of a last ditch effort sort of thing. The best thing to do is take the block to the machine shop and have the main housing bores opened up and the big ends of the rods opened up as well.
As for filters, the PH series fram filters have no place on anything performance. The TG filters are closer to a WIX type filter and I'm not afraid of them as much. Is the plug under the #5 main cap that directs oil to the filter still there? That'll cause low oil pressure.