Bosch plugs seem to have the blessing of most that have used them

Here are the numbers

289 Studebaker (Normal 225 Hp) - W8AC (Copper)  W8AP (Platinum)
                                          (sgundry@aol.com ) Jul2000

289 R1 / R2 Avanti -Champion J12Y equates to  a BOSCH WR9FC (copper)  WR9FP. (Platinum - Jan 2001

Torque plugs to 30 ft. lbs.

The cross reference is at http://www.clubplug.net/cross.html