Bouchillion makes a 6 blade that replaces many/most 60's/70's fans. I'm running one to replace a MP viscous fan/clutch kit that ate a full tire tread. Its listed at 18"... can compare to your current one. The standard fan on a late 70's and maybe some 80's RWD MOPARs will often fit also (junkyard).



http://www.bouchillonperformance.com/mechanical_fans