Hi,
I 'had' a set of Terry Shepherd 500 conversion barrels and pistons to go on the NS/RGV, but they got broken by a courier.
A few guys on the NS400 forum have got 500 conversions. The only dyno chart I've seen was 70 bhp - Although someone told me they had a dyno trace for 90.2 bhp, but I haven't actually seen it.
Mat.