Not sure if all of these people do CVH rebuilds so forgive me if not, just know they have good reps.
Motorsport Development
Karl Norris
Grove garage
Burtons

Like I say some of them may not build engines but its worth asking, also ask around and get others opinions as you are on this post.
We can build the engine for you but we are still new and have no real rep as such to speak of. We are currently rebuildin 2 mk2 XRT conversions and not so long ago rebuilt my own 190 bhp S2 and a friends pretty std FRST.
If you would like a quote please PM me or call

Also you may need a new block depending on how bad the step is and whether its been rebored previously.

Cheers
Jay