I'm wondering just how much of the 6.6 really is a direct swap into a 7.8? I hear they are the same motor except for block height and stroke. More specifically, I have a 6.6 with 40K miles and it looks almost like a new motor but it's just too gutless for my needs even with the IP turned up. I also have a 7.8 which is no powerhouse but it isn't the absolutely slowest rig on the road, but it's high-mileage. The 7.8 has decent blow-by and smokes a fair bit after it's say overnight. So, I'm hoping I could swap at least the head but hopefully also have the option of rings and pistons, etc. from the 6.6 to the 7.8. Obviously if the block is really tired it's time to bore it and oversize pistons, but if I could freshen the motor up with nothing but a couple gaskets and some motor parts that aren't doing me any good anyway, that would be great.