So whats this kind of swap cost to do???

I think it can be done pretty cheap if your willing to take on alot of the stuff yourself. Good 5.7 hemi short blocks are cheap but be careful not to buy something thats had the pistons broken as thats pretty common. There are plenty of good 5.7 hemis around at a reasonable price. You can use the jeep GC manifolds or I've been modding a set of Jeep SRT manifolds and just about have them clearing but it's been alot of work. Really the engine managment is where the money can be saved or spent. I really want to make a stock truck PCM and wiring harness work so I can keep the fuel injection and tune it with the Diablo CMR software. Almost certian I can do this I just need to.

It's not as simple as dropping in a 340 but doesn't necessarily have to cost more.