Ain't that the case. You could have a step van full of tools and still not have what you need.
I found a good technical manual covering the Peerless trannys including torque values for the bolts. But I did not see the actual head sizes listed.
http://www.smallenginesuppliers.com...eh/Tecumseh_Transaxle_Service_Information.pdf
http://www.smallenginesuppliers.com...eh/Tecumseh_Transaxle_Service_Information.pdf