It took me sometimes to answer but...
Ok lets say you decide to produce a 24 pdr siege gun of Gribeauval design.
This kind :
I can provide different source material like (here in low def but I can provide HD)
Painting photos, drawings :
scans of originals plans of the time
Overall and Detail photos of models
Overall and detail photos of actual guns
if you decide to make this 24pdr siege gun on his siege carriage, you will be able to reuse the guntubes to make a fortress gun of the same era
if you re-use the carriage you made for the 30pdr parrot gun of your acw range (with some minor changes), you could provide a french siege gun of the Valée system used in all the french campaigns between 1830 and 1870 (Algeria, Anvers siege, Rome siege, Crimea, 1870...)
your carriage of the parrot gun
a 24pdr siege gun of the french Valée system
if you re-use the carriage you made for the 24 pounder siege cannon on barbette of your acw range, you could provide a french fortress gun of the Valée system used in all the french campaigns between 1830 and 1870
your carriage of the 24pdr ACW gun
a 24pdr siege gun of the french Valée system
Here is what you can produce using one model of a guntube, making some new carriage and re-using some stuff you already made, it seems to me its a good deal...but I'm not in the business
If you are interested, I will love to you help you by providing such infos, but by mail as there are some photos of my own private collection and photos of pieces not shown to the public in museums that I cannot show in a public forum (I work in military museums so I can sometimes have acces to some piece no more in public display)
Hope this helps