I owned a 95 351 SD Truck and I now have a 96 351 MAF Truck.

They both have always had a slight rough idle. I've actually learned to like the slight roughness. I think of it as feedback from the truck. Just like listening to the tires, and feeling through the steering wheel when your cornering.

 

This one definitely does not have a MAF Sensor. I don't recall whether the other one did or not, but it very well may have been a California '96.

I'm going to pull my boat this weekend up some pretty steep canyons for the first time. As long as it pulls well without any issues I can get over the idling issue.

 

I took it out tonight and it seems to have stopped pushing the antifreeze out, into the overflow. Yay! I'm sure it was the spring in the 18yr old cap.

Still running rough at idle but runs strong all the other times.