Hello, I converted to HS6 on my 63 TR4. I picked up a set for my 72 6 but decided to go with the Hitachi HS6 version so I had the set just sitting there. I am using the original manifold. Really dont care about performance. Just looking for reliability. I have had some issues with the H6 leaking here and there in my 3. The HS6 seems to be better in that regard. Bob