For the general measurements I went to my local weaving supply store and just measured as many aspects of the Ashford 4-shaft loom that I could. The castle and loom frame are all 1x4s and the rest are 1x2 and 1x1. These are the heddles I used: https://www.yarn.com/products/leclerc-texsolv-heddles

After using it to actually weave, I've noticed that the string entry holes at the top of the castle should all have been sanded ultra fine to reduce any wear and excess friction on the string. Also the popsicle stick beater was basically useless and I had to pick up a second-hand metal one.