What to use to clean tranny lines?

I wasn't thinking and during the engine swap I got all kinds of grime, oil, fluid under the car. Of course that's were I left the transmission lines laying in the filth.
What can you use to clean the line? Someone said to tape up one end and use gas to go through them. Any other methods?

I was looking into new ones, but all the new lines say 340/727.
I have a 904. Are the connectors the same size?

Thanks!