immortal1 (linn)
+1y
The ones with the plug on the top are preffered, but not required. You can add oil thru this plug, but the SANDEN compressors will pump it right back out as the cylinders are mounted horizontally. The York compressors have the cylinders mounted vertically and adding oil to the pump works much better. With the SANDEN, you should figure on adding an inline oiler to the intake side.
Also, I believe the 508 and the 708 have / use the same mounting brackets.