On that stroke motor advertised I couldn't find out whose heads they have on it. That is something I would want to know more about I think. If they are what we commonly call Chinaheads, I might pass on it unless they took the out of the box heads and ran them back through their head shop, verified that the seats and guides are right and they don't leak. They do sometimes leak right out of the box. They might have cheap junk valves, springs, retainers and keepers and that is something you never want to cheap out on but engines like this start with a dollar figure or range of dollars they think they will sell for and engineer backwards.
Also, they claim 460 horsepower and I have limited experience with crate motors BUTT and it is a big butt. I helped drop somebodys crate engine in a fox body and it was supposed to make 400. We figured it at around 325 so its a buyer beware sort of a situation. The builder can also always say that you didn't finish it with the right stuff or something.
Warrantys are great BUTT, another butt. If something goes wrong you have to crate it back up and send it back and I know of cases where a crate motor company wouldn't make it good because they came up with all manner of excuses like you didn't run it in right or you ran it hot or ran the wrong oil in it or you spun it up way too tight or on and on. If a company wants to, they can wriggle their way out of any motor warranty easily.
I would also want to know the complete cam spec's. It appears to be either a 5.0 or 351W due to the firing order.
I would also want to know whose stroker kit is in it and what static compression it is making. Whose ring and bearing packages did they use, what vintage block is it and what machine work was done to the block.
Are these engines dyno tested? I wouldn't buy a crate motor that was not run and tested.
It is a 28 oz external package but was it professionally balanced and was it blueprinted? I wouldn't build something like this if it wasn't and I didn't. I paid to have my assembly professionally blueprinted and balanced to tighter than plain old throw the engine together specs and balance numbers. The rings are all file fitted and matched to the specific piston and cylinder they went in. All the spec's like piston to wall clearance are dead nuts on, bearing tolerances, it is zero decked which was part of the compression number I wanted to hit with it. My shop also decided to do an additional micro polish on the aftermarket crank because the manager who hovers over all my work didn't like what he saw out of the box.
There are just way too many unknowns. I would never buy a pre-packaged engine in a box. I might pay a shop to build one for me and have me involved in all the discussions and considerations on how it is going to be put together. I would also want to supply all the parts so I know what is going into it.
This is just me talking BUTT, another bigga badda butt. There are these.
I found complaints going all the way back to 2008 so maybe they have cleaned up their problems or maybe not. It also was suspected in some of the discussions that ATK doesn't build their stuff. It is thought that they contract out the builds and just sell them so if that is really the case, what sort of quality are they getting and if they are not dyno tested, what are you getting?
I don't rain on stuff like this for no reason and it is not very pleasurable to do it but you have to be careful with your money and engines in a box that you know not much about are an area with a lot of potential to not get your money's worth.
It would very likely come out a lot better if you picked a verified reputable engine build shop that builds to suit the customer specifically that they are building for.