Here is a diagram view of the parts for this unit and options you have. This is a good diagram to keep, so you can order parts later. The option on this is having a high pressure seal. This depends on the load and job application you needing to deal with.
Some of these parts are set at factory defaults, so consult with someone before you can something. It could effect the outcome of the unit.
Also there is a model code diagram that shows what each letter or number means. Like how many pistons you may need. So keep up with your tag information.
If we can help with repairs or parts, give us a call at 662-871-8403 or 800-361-0068