Leovinci exhausts for camino are hard to find, proma circuit exhausts are still sold new (if you look hard).
The exhaust you linked to is a SITO exhaust, thats almost the same as a standard camino exhaust and will not give you good speed.
H1-4 and P1-4 are types of 49cc cylinders, the fastest is a P4 the slowest a H1 cylinder.
But 70km/h is to much to ask even for a P4, for that you need a bigger cylinder, like the polini 70cc you linked to.
A Leovinci exhaust for camino here:
http://www.camino-tuning.be/www-tuningschmiede-f40/
look for: HONDA Camino LeoVince
And Leovinci here to:
http://www.scooterenminibikeshop.nl/ind ... 95&lang=nl
Proma GOLD here:
http://www.camino-parts.nl/uitlaat.htm