TF 904 New Oil Pan Question

You do not need a spacer or extension. All you need to do is use enough transmission fluid to show "Full" on the dipstick (checked with the engine running, transmission shifted through all gear positions twice and left in Neutral). That will take more fluid than the shallow original pan took, but once you've added enough fluid to bring the level up to "Full", all you have to do is maintain it there -- which requires doing nothing at all as long as there are no leaks. The only reason for needing a spacer is if you are doing extremely aggressive racing that would tend to slosh all the fluid away from the filter at its normal location. The fix for that situation is to install a deep pan with an extension so the filter is always below fluid level even when it is sloshed. For any kind of street driving, the extension/spacer is not necessary because there's nowhere near enough slosh to uncover the filter.

You must use the correct 2-port filter as described at the linked article. If you do choose to install a spacer/extension even though you don't need one, it must be a 2-port item.