CBRF Engineer- Try getting a scan tool on your truck and see what it reads. Sometimes those gauges arent always on the money. If you also have electric fans id check your fan relay and make sure those electric fans are kicking on when they should be. If you just let it Idle some more after it creaps up to the 3/4 mark will it keep going to the red??? Or does it eventually kick the fan on and take it down to around where it should be? Put a piece of cardboard down under your truck at night. That'll show you if the leak is coming from your truck, and where abouts its coming from.
Riche- I dont really know if the 454 would have the same problem. I would assume so cause I heard the intake problem was related to the gasket itself. If they got all thier gaskets from the same manufacture and they were made out of the same materials I would assume they could have the same problems as the 350. Just what I think though.