From a post on the VTXOA tech board
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pick one.......
Spark plug cross-reference for the VTX
GAP 1.0 - 1.1 mm (.038 - .043 in)
Manufacturer
OEM
(03+ stock)
Cold
(02 stock)
AC Delco*
41-806
41-801
Autolite
APP3924
APP3923
Bosch Platinum +4*
4419 Stock '03 hot for '02
4418 STOCK '02
Champion Copper*
RC9YC4
RC9YC4
Champion
-
7346
Champion double platinum
-
RC10PYP4
Denso
VK16PRZ11
VK20PRZ11
Denso
-
PK20PR11
Denso Iridium*
-
IK16
Motorcraft
-
-
NGK*
IFR5L11
IFR6L11
NGK Iridium
BKR5 EIX-11
BKR6 EIX-11
Splitfire*
SF522D
SF392C
Splitfire platinum*
TP522D
TP392C
Uber Power*
FZX5iL
FZX6iL