Castrol EP Gear Lubricant 320 is or was manufactured by BP Lubricants. 

In this cross reference tool, PSC offers this Castrol EP Gear Lubricant 320 and/or equivalent products of the similar quality and performance.

See below for the equivalent products and select the 'View Manufacturer Info & Data Sheets' tab for safety data sheets, as well as product data sheets to compare specifications, approvals, properties, and performance characteristics.