Figure this would be a good place to start, I recently purchased an 1983 F250 with a 2000 Cummins and NV4500 swapped. Running the Dodge brakes, cluster, etc.

Currently I removed the stacks and installed a Magnaflow system under the truck- 3.5" down to a 4" pipe all the way to the rear tire. The system was for a 98-02 Dodge and fit well under the Ford, I did need to oblong the bolt holes in the exhaust flange to get the down pipe to bolt up.

Also removed an undersize air filter and replaced it with a 'BHAF' and replaced the welded 90 degree 4" intake pipe with a mandrel bent 60 degree pipe.

And pictures:

How I got the truck-

I always liked the 80-86 fords. Good luck with the wiring. Found out about a new kind of butt connector from a CAT guru who was tracing down some internal wiring probs on the big truck I drive. He said they have glue in them and when you take the mini torch to them they seal up real good. Said he got them at Wally World. They work inside the valve covers of a big cat and keep the oil out and resist vibration so I don't know why they wouldn't keep out water and moisture.

I used to sell some butt connectors that had heat shrink tubing around the outside and a small tube of solder inside. Put your wires together, use your torch and heat them up, it shrinks down and melts a little solder into it all at the same time. They were made by Standard Motor Products. Very nice easy splice and seals up good.