From an installer and troubleshooter perspective a connector on the firewall is the best way to go.
There's some nice steel connectors available for fire resistance or the ol' standby, circular amp connectors are less expensive.
Most of the signals from the engine sensors are analog so they shouldn't be affected by noise issues and shouldn't require shielding, in fact Electronics International and Grand Rapids Tech don't shield anything from the engine.
If a shield is required simply carry it through on a pin. You could also gang all shields on one pin except the mags shield ground, this must be separate to keep the mag noise off the rest of the panel wiring.


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Jon Hadlich
AI Systems
(541) 815-7381