There is a detachable drum mag for the sks its around $300. The AL drum mag won't fit the sks unless its the sks that takes "AK" mags then you have to cut the stock to get it to lockup. Unless you weld a spacer on the ak drum mag to extend the loc up lips higher which could be done.
BigBill
I believe the BATF laws state if we modify a mag to fit another gun it must still fit the orginal gun it was manufactured for. The sks is the most reliable with the orginal ten round fixed mag. but I have seen the detachable 20rd and 30rd mags function flawlessly too. The only problem with the larger mags I have seen is some guys try to run them dry. They have to lube the inside if the mag so it pushes up the rounds freely. I think it was the only drawback with the sks was it capacity and a ten round mag in full auto mode was just impossible besides the slower manufacturing process with the solid steel reviever.