No that kit is not for your monitor! The 7400 and 7500 are completely different than the k7000 series.
The k7400 and k7500 are current production models and as such, you have to purchase from Wells-Gardner or one of their authorized distributors such as Happ Controls, Betson-Imperial, Mazzco, Amusements Plus, Penn-Ray, Competitive Products, etc. You'll have to bite the bullet and make the minimum order requirements. Maybe you have some friends that might need some parts from the Wells-Gardner parts dept and you could pool an order?
I've "heard" that Bob Roberts is starting to sell his own version of this kit now, but I can't verify that for a fact. By the way, the 7400 and 7500 use the same capkit.