You will need a finished head/shoulderplate assembly. I used GB-124 and GB-124S molds. Contact https://bellcollection.com/ for further information. However, any shoulderplate/head assembly will work. Here are the approximate measurements (with leather bodies you have a certain amount of flexibility- no pun intended). You need also good leather (lamb skin or any leather that does not stretch too much and resists tearing) and sawdust or cork for stuffing. The body takes time and care but it is well worth the effort. You can leave the separate toes out, but the movable fingers are well worth doing! Much nicer than porcelain hands.
Shoulderplate across shoulder/shoulder - 10 cm
Shoulder plate depth (center front to center back) - 6 cm
Shoulderplate height (center back to socket edge) - 4 cm
Head circumference - 17.5 cm
