OK. You can put an adapter, available at most speed shops, on any of 3 spots on LS-1 locations. Behind the intake, left hand side of the timing cover, or above the starter. The adapter has a male M16 x 1.5 thread converting to female 5/8" x 18 UNF thread. You made need an additional fitting to that to match the oil line fitting.
I have not done this, but a friend researched it for me. I would ask your local speed shop too.
Hope this helps.
