When you have to replace the inline hydraulic filters of the Main Cargo Door on a modified -300 or -400 aircraft it is possible that this system uses Swagelok filters. There are 3 filters (press, return and stby) installed in this system, which is installed on the LH wheel well aft bulkhead. The replacement instructions are hard to find (or not findable at all) in the AMM. Swagelok has their own service instructions which u can use.
Click here to see the PDF file from Swagelok.