Muscle is decent, but you still have to check things. I've used probably 10 440Source kits over the years that always had the same issues (or details I considered issues). I've only done 1 Muscle Motors kit and while I was impressed witht he finish quality of almost everything - the chamfered bearings were not chamfered enough and the assembly would bind with both rods on the throw. This was a 383 based kit too, and there was a long (months) wait with promises of pistons that were not shipped for a while. Minor things in the big picture but enough that I wouldn't say it's ready to go out of the box.