I have the truck, so it is all there. Flywheel is cracked but that can be replaced easy enough. (motor/trans already removed) I was asking in terms of reliability and what kind of cost comparisons in improving on power. I know most parts are interchangeable but I would think the 350 would have less expensive parts inside as the 350 was produced in much larger quantities. On the other hand I have heard(and read) both good and bad things about the 400. Also, in checking prices it seems the 400's cost quite a bit more if one was to buy a complete motor.