I used a racetech 5kg with collars but had to do something about it rubbing on the air thing. There is an ebach one that fits "BUT" it starts at 5.8kg.
I ended up getting two springs wound by king springs in QLD the same size as the original in the weight I wanted. They came in any colour you want that is yellow.
Im a few kgs heavier than you but only calculated my spring rates front and rear at a low rider level and enduro using the ractech calculator.
The 5kg spring only has about 7 mm of pre load on my shock to give me the right sag. The original spring with like about two inches of pre load was WAY too soft I think it was made for my eight year old.
The shocks are also only charged at the lower recommended pressure of the spec and filled with 5w oil. They have MSR or All Balls seal heads that are easy to get. The orings are easy to get from CBC bearings. The little one on the end of the adjuster shaft is a little tricky but shoiuldnt be to hard following the manual if you have one.
If you go a gold valve you will need someone to set up the washer stack unless your willing to trial and error it.
The final spring rate will depend on whatever your going to be riding, motorcross enduro trail
Rebuilt from head to toe the best money I have spent on my bike has been the money spent on suspension.
From a Vinduro perspective comfortable plushness with bottoming resistance makes it a pleasure to ride for two days. Its all about the wheel staying in contact with the ground over the terrain. VMX is a different thing and would want a stiffer setup.
