I've heard conflicting information about this. When the roller motor came out in 85, the heads were basically the D9 head with the big 69 cc chamber. What I recall was that these heads were slightly modified to allow the roller tappets to be replaced with the heads on. Earlier heads install on a roller cam motor didn't have the needed relief. Now that's what I've read more then once. Recently I've been told this is not true. Since I haven't personally tried with early heads, I can't say. I can say on my GT40P with heads on. I removed the tappets and reinstalled them no issues.
