Problems during/after Header instal

[brassnut]

Now that I have the oilpan off, I decided I will buy a new one and use the driver side dipstick tube . When looking at oilpans, I see that they are made for 1 piece and 2 piece Rear main seals. Forgive my ignorance, but where do I look at on the engine to tell what type RMS I have? Does the new oilpan or gasket have to match my RMS type, or do both?

Thanks for the help.