Don't get confuse with the XL. It had the twin down tubes later on. I did not know they made one for the sl. The XL had black pipes , two on side.I was pretty sure that both the cb and sl had the same frames....of course I have been wrong before. Ask my wife I had to marry her 3 times to get it right....still not sure.
I was sitting here thinking that something was wrong. I think it was me as I remember that it was the cl that had the pipes coming up on the left side. The sl and the xl are different bikes. The bike you got is an sl. I know the one I had bought new in 1970 had a different paint pattern and different color blue.
Well now that I am all confused again , Iwill have to do some checking.
Boy was I all wrong. I had to go and find the pictures. My 1970 CB350 had the different color and all. The 1970 SL350 is the same as yours. Same color and everything. Wish you were closer. Do you have a title etc. Maybe I will sell my 750's.
Ron