What're you tryin to do?

If putting newer pencil plug engine into older loop plug chassis, then you'll probably need the relay system too.

Older style loop glow plugs mainline mainline through fused ignition switch/hotwire from the battery, but newer style have electric boosters in the system - that's just my take.

Never attempted such a swap myself but I'd be reconnoitring exact replication of newer pencil plug electric system, as close as possible.

Hell, maybe getting the 'upgrade' install kit for loop to pencil plugs.... then using the wiring and throwing the rest of the kit in the trash might be the answer.

Am assuming you are putting newer engine into older chassis.