What I did is I took the six digit serial number from the block. This is located on a flat square right at the end of the block near the bell housing on the exhaust side. The serial number is etched into the block so you might have to clean off that area to see the numbers.
I then found out which cars my engine might have come out of. Since I knew mine was a non-neo rb25 I narowed it down to ENY33,GC34,GCC34,GC35,GCC35,FY33,ECR33, and WGC34.
Then I just started putting the different possible combinations into Fast until it gave me information. Usually it will say VIN not found or something like that until you get the right one.
Hope that helps.