E30 Zone

I have a 316 shell with 2.5 conversion but the speedo and rev counter aren't working. I know this is a common issue when converting from a 4 cyl to 6 . Just wondered what parts i need to sort it ? Wiring loom from 2.5 etc ? This has probably been covered before on previous posts. thanks

that also includes getting the fans and heaters working inside the car . apologies if this has already been covered .