my guess, and it is just a guess, is see how it is described as a "kit"? The core would be the same but the piping of this alleged "kit" would be a different pathway, although the piping diameter could, or may not be, or may be similar to, the same size. Possibly 64mm.
Re "What should they be for an R33?" , I would estimate, with no legal claim of specific knowledge to, or of prior events pertaining to, the piping contained in "Blitz Intercooler SE Kit - Nissan Skyline ECR33/ER34 - Part No: 23100", being as suitable for application to an R33. Or more specifically, an ECR33.
Hope that clarifies everything you needed to know, without searching the forums for the answer.