If you've come across an 8" Toyota front diff that leaks from the gasket between the axle housing and the diff carrier, it's almost always loose nuts or even studs. This is common in the Toyota truck world.
These are JIS serrated flange nuts, class 10.9 and zinc plated. It takes 10 for an open front diff. Studs are class 10.9 to match with the serrated flange nuts which are also a class 10.9 or a grade 8 equivalent. Stock Toyota were one grade lower.
Included in the instructions are for open and locked diff applications.