www.pdm-racing.com sells 91 camshafts and so does nissan motorsports (NOT nismo thats a whole diff company).

jwt sells only SOHC cams and JUN sells cams only for sr20s. there arent many options out there.

the 91 cams give u about 9-11 wheel hp and tq and are priced decently.

might want to check www.courtesynissan.com as well they carry aftermarket but havnt checked to see if they sell cams.

EDIT: courtesyparts.com has nissan replacement cams as well as a race cam but one of them requires different CR pistons.