Thanks for your response. It currently has leaf springs lowered by 1" and "I think" standard springs at the front because it is lower at the rear.
From other photos I see that the sill is parallel to the ground or slightly high at the back, correct?
I found for sale on CJ some 5-sheet crossbows with original height defined as "heavy duty". I think they may be the most similar to mine, even if they don't have colored stripes like the originals, for me it's already sufficient.
Here in Italy there is no interest in doing auto concourse, it's me who for personal pleasure wants to reproduce the original as faithfully as possible. As soon as I download the photos onto the PC, if you are interested, I will publish some photos of my work.