I have a 1989 350 block from a fullsize pickup. Im putting the Comp Cams XE274 cam in and when I went to bolt up my timing chain (part number clo-9-3145 on Summit)the bolt pattern on the cam gear was smaller than the pattern on the cam. I ran the part number figuring I had the wrong timing chain and it said it was for small bolt pattern cams. I never knew there was different bolt pattern cams on small block Chevy's. This timing chain correct for the block I have but not the cam. Now I am confused as to what timing chain I should get? I want a true double roller. Thanks.

Sounds like you got the factory roller cam timing setup.
You need the non roller timing set