Thats probably the casting number, I've not had much luck looking these up. it makes no odds either way which head you have, they will both fit.
The only real difference is the early ones had solid lifters, and the later ones had hydro. Easy to check, if one of the cam caps is missing its a hydro head. The other thing is that K-Jet & Digifant heads have different injector inserts, but you can unscrew them with a suitably sized allen key & swap over
