I wish you luck!
Just went through this recently, first bus I ever did. Through research trying to find templates learned this: Busses are not produced by standardized methods like many other vehicles, school districts in different areas have different requirements and standards can change several times during a production year... depends on the production run and who its for, about the only thing standard is the hood. For this reason templates are hard to come by, and if you're lucky enough to get your hands on one (I hope you can) verify that all dimensions are correct before you start using it. We ended up doing it the old fashioned way, lots and lots of measuring....