I have a simular motor that I just built that came out of 90 model 3/4 ton truck. It has 1-piece rear seal but no provisions for roller cam. So far all roller cam blocks had the 3 bolt holes tapped. Also along with what the others said, the late models (1-piece main/roller) have to have a different flywheel/flex plate as the bolt pattern is smaller. If you do have a roller motor, I think I have a new ZZ4 cam, lifters, retainers, spider and pushrods. I think you also need to use self aligining rockers.
Hope I haven't confused the issue. If you only have two spots on top of cam I don't believe you can make it a roller motor.
Jim