Both relays should be available and from the info I just looked at both should work just fine. For the rev limiter to occur at 4000 I would think you have a 4cyl relay. The rpm limit should be on the side of the relay but the relay doesn't wait a minute to count rpms, it looks at the frequency and divides by the number of cylinders.

6000rpms is 18000 firing events in a six; it is 12000 on a 4. 4000 rpms on a six is also 12000 firing events.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician