Originally Posted by Twix

In stock form, the first gen 4.6 SOHC makes more power than the rover 4.6. I have a first gen in my T-bird. Swapped the heads, cams intake plenum and put shorty headers on it and I was running 300 WHP. That's more power than needed for these Rovers with a driveline that will most likely shatter with that kind of power.

The LS is definitely a better swap. Cheaper and will fit. The modular engine is monstrous in size, and will be more expensive to get power gains.