Hi Alex,
The biggest problem installing one of those adapters is getting a really good seal under it, where the oil cannister originally seated into a groove in the filter head. Perhaps the most important thing, just as with that original cannister, is to make sure the old square-sectioned rubber sealing o-ring is removed before installing the new that came with the kit (forgetting the old one in there and accidentally stacking a new one on top of it nearly always causes heavy leakage). Also check that the adapter is seating squarely within the groove and not hung up on any edge.
I think those adapter kits sometimes come with two different center post adapters, because TRs had two different filter heads with different threads there (Teculmet and Pur-O-Later, if I remember right). One or the other of the adapters will fit. Just be sure to use the right one.
Also, those center posts of the adapters are usually brass, so be a little careful not to overtighten and break it.
I think the Fram PH3600 (and it's equivalent in other brands... I use K&N HP-2005) is pretty standard for these adapters, but to be absolutely certain you could take the adapter with you to the auto parts store.
Oil filters are much more standardized than people tend to realize. The industry seems to take great pleasure in serving up a huge range of filters and printing up thick catalogs with very specific application info. The primary variables among filters is the size of the threaded section and whether that thread is metric or SAE, plus the diameter of the sealing ring on the filter. The only other key consideration is the length and diameter of the filter cannister itself, if it will physically fit in the space available in an engine compartment. TR2/3/4/4A have lots of room in that area and can actually accommodate all sorts of filters.
Once you have determined which of the center posts will be used on your car (compare with the bolt thread on the original TR fitler cannister), before installing the kit just take the adapter parts with you to the store. There you can simply test fit to your heart's content, checking various filter's threads with the adapter post and comparing the sealing ring on the base of the filter to the flat area of the adapter it needs to seal against.
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