Turbo 400 trans filter

[howdies86]

I need a trans filter for a turbo 400 that picks up fluid from the rear. Any vendors and part #s? Also I have one for you. Transmission has manual shift valve body, with a brake. When the trans is shifted 1st to second, it immediately shifts to third gear,skipping second gear, Thought it was the rear sprag so we changed it. Nothing changed. Shifting on to third position ;still nothing . Caint find. anything wrong with Clutches, bands or seals, Valve body and case are flat and no gaskets are used between plates and case . CHECKed line pressure and found no leaks. any suggestioons??