You're confusing lobe separation with intake center line. Lobe separation is how far apart the intake and exhaust lobe peaks are in degrees. That's where the 108 and 112 come into play. You have either one or the other. That measurement is ground in and cannot be changed....without regrinding the camshaft.
Intake center line refers to "where" the camshaft installs in the engine and is generally 4 degrees advanced FROM the LSA. So, if you have a 108 LSA camshaft, you would install it at 104 intake center line. I would probably go on down to around 100, because that 508/292 on the 108 is a cylinder pressure robbin sumbitch unless you have a pretty high static compression ratio. But it can be made to run well if advanced properly.