The Grandt Line range has been taken over by SanJuan Details.
The former Grandt Line website is currently still active with full listings of the components they produced.
One way of searching for components is to download PDF documents that summarise the relevant ranges, with dimensional details. These do not cover everying that is produced but cover some of the most popular groups of components under a series of headings. Click on the links below to open the documents, which can then be downloaded.
The new website (the relevant section being at https://sanjuandetails.com/model-railroading/o-scale/) is including an increasing number of the items. Reference numbers do not seem to be changing.