Flywheel Double mass Vs. Single, I or E

[lokillo]

I just would like some valuable info. on flywheel type and clucth kits. since there are two types of flywheels with E30 and different clutch kits for them.
I already know that double is more hevy than single, but in specs any detailed info that I should Know?? && And &&

I haven't figured out witch one is installed on my car, I just got it recently and I am having some issues with a big oil leak. I belive is the rear main seal and/ or the oil pan gasket, I figured I will change both since I have to remove tranny. But Before I remove my tranny I would like to know witch flywheel to expect since Im considering buying a light one and/ or new chutch kit at least. My car is a 88 325 IS Std. tranny. Thanks!!