Cut and weld the steering arms you have. That's what building a car is, making stuff fit, not running out and buying a kit, to me anyway. Yeah, Yeah, a lot of guys start fidgeting around when you talk about welding steering components but if it's done right, there shouldn't be any problem.
I think the lower steering arms are the only part of my front that I haven't welded on. Axle and both tie rods were sectioned, and the steering arm on my pitman side was completely reworked and extended to get my geometry right. I have built a lot of pitman arms over the years to make the steering geometry right when installing power steering on older cars. I've never had one fail. I tack, measure, steer side to side, measure some more, usually cut, reposition, tack, all the process until I like it. Then take your time welding, keep the inter pass temperatures down. When you think you are done, grind/polish with a flap wheel and if you see any undercut, weld it up until you can polish the part and not tell it was ever welded. And don't even think of using a wire feed to do it, those welds are too brittle IMHO. It's the old lincoln pipeliner and 7018 for anything structural or safety related on all my fabbing. It's ok to tack with a wire feed though. I've even done them on an AC buzz box, you can get AC 7018 rod.
That kit looks like junk, I wouldn't put something like that on anything of mine.