There aren't any ksc2690 on the schematic.
If the ksc2690 are in place of the ksc1027, yeah, sure. 3520 are higher voltage, may have a little higher Cbe but probably should work.
Incidently when subbing ksc for 2sc parts, use the fairchild datasheet, not the sanyo or toshiba one. Some parameters may be different. I found it on datasheetcatalog.com.