Stroker 440

440 Source is good value - but parts need to be carfeully checked by the builder and I always add on a little for fixing things.
Muscle Motors are decent kits for the money. They didn't chamfer the bearings of the last one enough but I do that anyway so no biggie.

Most kits use the same parts and have differing levels of inspection and finish quality. So choose what you feel delivers the best value. In my opinion, in no case should you have the kit balanced unless it's a shop like MM. Buying components in sealed boxes you should have every part carefully checked, and account for more labor to assemble it.