Jonathan,
Congratulations on your new Tartan 33.
I own Kelpie, a 1980 T-33 #73. I am replacing all of my 40 year old portlights with Beckson 414 portlights, which are drop-in replacements. The screw knob closures have been replaced by lever closures, but otherwise they are virtually identical. I chose these over metal replacements because I knew they would fit exactly. And Defender had them on sale.
Re the lexan (?) hatches, I plan to get a headlight lens polishing kit and refresh the lens. Maybe I'll prime and paint the frame, but no plans to replace.
Good luck with your project. If you plan to replace the fuel tank, which I did two years ago, I can recommend a fabricator and send you the dimensioned drawing in pdf.
Best regards,
Larry Luck