I've used import car parts for loads off stuff on my Subaru based not too far from me so delivery is always quick and all genuine parts. And there quite cheap as well. You can't go wrong with oem parts I would stuck with oem for timing belt kit or a reputable aftermarket kit such as cosworth / hks etc. As for the clutch depending on what your future plans or to give it more power etc. Put a stage 2 one in then you won't have to replace it again if you do decide to get more power.
Stunning looking car my mate just got a red still 300 one of these last week. I love it. hope the project goes well !
Also first thing I would do to your still is paint the front grille satin black just my person preference but done my mates on Saturday and it looked much hetter. I'll add a pic below.