Wrong spark plugs???

I have a 1999 Vitara, I bought new plugs for it, NGK BKR6E-11, which is what the owners manual and Chiltons says it takes. I took out one of the old ones, it is an ACDelco R45TS. The NGKs have about 3/8" more threaded area on them, I don't want to poke a hole in my pistons!!

Any help on which plugs it should be? I normally go by the books but this is a big difference in how far they will go into the cylinder.

I bought the Vitara used about a year ago, this is the first time I've had a plug out.

Thanks.