I've tried out both the BBK 1700 and the Ford Racing one on my Ex with SOHC 4.0 (both are 70 mm TBs and are designed for the 4.6L V8s). I would have stuck with BBK exclusively, but the shyster that sold it to me on eBay neglected to mention that the idle adjustment screw was sheared off. I'm trying to get another screw from BBK right now. In the mean time, I found a good deal on the Ford Racing offering so I scored one and it's on my Ex now.
Some observations.
I don't think I achieved a lot in the way of HP but maybe a little. I felt the same way when I put a C&L MAF body on my Ex a few months back. I've heard others say I might lose a little bottom end, and that's possible. I do feel a bit less torque, but it might be psychological. However, I definitely feel a new smoothness in acceleration and a more lively feel at higher revs.
A downside I have found with both the BBK and the Ford is that my cruise control seems a bit whacked and I haven't spent much time trying to fix. When I set the speed I want to cruise at, it doesn't seem to hold that speed very well. When going up hills, it definitely drops a bit too. I'm still working on figuring out how to resolve that, but I don't use cruise much anyhow so it hasn't been a high priority item. If anyone has any theories as to why my cruise is wonky now, I'd love to hear them.
It's not the cheapest mod around, but I do like the change. I guess I just like to be different and as much as a lot of people are giving theoretical reasons why a larger TB is not an effective mod, I'm happy with this upgrade overall.
When/if I get another idle screw from BBK, I'll probably put it up for sale. I prefer the Ford offering because it does come with a TPS. However, it didn't come with hardware or a gasket. The BBK offering does, and it's also a nicer looking unit and seems more refined than Ford's. I'm not really worried about the cosmetics because the TB sits under the engine cover anyhow. My guess is that both BBK and Ford perform the same.