I would like to install my heads on my engine. Car is built 12.98 .. 3,8 Liter V6

What do they mean by that?

Cylinder head bolts:
1998 and earlier
Step one ....37
Step two Turn an additinal .... xxx
Step three (center 4 bolts only) 30 .... What do they mean by "center 4 bolts only" ..?

 

what manual are you using? this is what I see in the 3.8 manual found here https://www.mediafire.com/?40mfgeoe4ctti

 

1,2,34.