I have a set of 4 NGK plugs BKR5E IX-11.
They are opened and were installed in my car for about 10 mins and then taken out. My engine has high mileage and didn’t run right at all with these plugs. $20 for the set. Paid $40. PM if interested.
these are the stock heat rating for the KA, you can try the BKR6EIX-11, it’s just one heat range colder, might be better for your application…
Price drop $15 for the set.