200/300 wiring matching

I'm getting ready to replace the bulkhead on my 200tdi 90 with a 300tdi bulkhead . Any hints for matching up the wiring what doesn't help is its an ex millatry 90 so I have some extra wiring for that and the wiring thats already there is for the n/a engine that was in it when I got it. The 300 bulkhead is complete with wiring all there , I relize that the conecterblocks are totaly differant so they need to be replaced.