I installed of gas lifts on the bed in my 183RB. I think the picture explains how I installed them and the only modification I had to do was to add the small blocks at the bottom of the lifts. Just make sure you attach them solidly (glue and screws) as they take the full pressure of the lifts all the time.
I estimated the lift required by propping the bed open with a board on a bathroom scale positioned at the point where I wanted to install the top of the lifts. then I doubled the weight because the angle of the lifts decreases the upward force they exert.
I used a pair of 67 lb lifts. With these lifts, the bed is easy to lift and lower, and it stays open once it is up with a 3" memory foam topper and duvet on top of the mattress. Even with the lifts, I still can't open the bed with my 75 lb dog lying on it and she is stubborn about getting off.
Here is a link to the ones I used:
https://www.amazon.ca/gp/product/B09...?ie=UTF8&psc=1