RE: Skidoo Rev XP snowmobile hop-up
Front shocks are ancient. They are from a Vintage "Marui Galaxy" , and fit like a glove. (google Marui-Galaxy RC buggy parts. Sometimes parts, like complete Marui Galaxy shock-sets, soft springs, hard springs and soft and hard pistons) come-up on e-bay pretty cheap, cause they are not as collectible as Tamiya vintage.) I had those for, like, 15 years, bought them for a monster-truck project that never materialized. I filled them with 300WT oil. Seem to be the best balance between tipping-over prevention and road holding. Current springs are the stock Ski Doo ones, but they are a bit too firm, though they look great!
-cylinder dia: 8mm.
-length eylet to eyelet: variable between 6 cm and 7 cm, depending on chosen piston.
-piston: standard 3mm - one-piece
I am still experimenting with several springs. Be forwarned though, They are a filling-nightmare, and the copper knurled cap will leave one's fingers raw.
To be honest, every oil-filled shock with a length of about 6 cm-eyelet-center to eyelet center- and a diameter of about 1 cm, or less and a piston of 3mm (for strength) will fit.
Moto-cross helmet is a repaint from a 1/6th scale Graupner RC toy moto-cross figure. With some searching in the 2-for one-bin at Your local Toy's are Us, it is often possible to score an action-man figure for little. They often have all sorts of cool helmets and gear. Figures are the right scale too.