I struggled to find all this info, so hopefully this will help others
Pop Top Struts
Mine was fitted with Nitrolift GS10-22-300-350. This tells you it has 10mm shaft, 300mm stroke and a 350mm body with a 22mm body diameter. It does not tell you about the rod ends or the force. The ends are 13mm ball sockets (which on nitrolift fit an M8 thread). The length of the ball sockets is 30mm from end to ball centre. In the UK SGS sell these and the socket is code B14.
Choosing a force. . .
What I found is that the stock seems to be 100lbf (444N). Heavy duty ones are sold at 110lbf (490N) and 120lbf (533N).
First off I got a standard which was dumb as I have solar on the roof. I had no idea what was fitted to my van initially and they were stronger than 444N.
I probably have about 10kg on my roof so second attempt was a 500N (112lbf). This works out much better but they still struggle to hold in the partially open state. I would go for 533N at least next time.
There are YouTube videos that show how to compress the struts with a ratchet strap and a prussic loop (loop of rope) this is really easy to do. Propping the roof is the bit that takes the longest (just finding something a good length). I used some camera rods with some books to space it all out.
Kitchen unit struts
The original struts had markings:
Google says this is a 40lbf (178N) strut with a 2″stroke- length between 5.5″ and 7.5″ (140-190mm). Think its 10mm ball ends, 6mm rod diameter, note that length includes ball ends.
At the time I got the van the struts had completly failed and I couldn’t find a direct replacement. I went for some a little shorter that were easily available on ebay and moved the mounting points. These were 80N small kitchen struts. They kept the lid open (apart from on a slope).
Eventually I put a magnetic knife block on the top so up-rated the struts and went back to the longer length.
I can’t find a UK 51mm stroke unit. Closest is under or over (40 , 60mm). Note that lengths of nitrolift units don’t include the ends.
Nitrolift GS6-15-60-100 rated at 160N (160mm long, 60mm stroke)
Plastic 10mm M6 ball end – 18mm length end to cetre. (complete length 196mm)
I managed to install these with the brackets back in the original hole. Took a bit of force to get them on due to the extra lenght. Work fine now, top does not raise by itself but will hold at any opening.
The knife block actually holds the knifes even over bumps etc. The block I bought wasn’t up to the job so I bought some Neodymium magnets of the same size, glued them on top of the existing cheap ferrite magnets and added spacers.