Well remember your speedo isn't gospel so it'll be anything from say 110 to maybe more than 123 as you have to allow 10% for inaccuracey.
120 ish sounds about right though - 8v and 16v had close ratio's so where never gonna win any top speed awards, but serious how much more would u want top end ?
Mine has hit the limiter just off the clock with 120mph clocks - unless yours has been *fettled* with that's your lot! the 8v peaks power-wise @ 5400 rpm so u'll need the wind behind you to get any more