4' high,2' round hardwood stump,use the other flywheels weight to shift alignment,(i'm talking real flywheels, not them pissy 2 smoke/gokart pizza cutter thingys
),as you get close,press them closer together,& repeat,dial guages between centres ,or V blocks for finished dimensions (hopefully),it's a bitch those last couple thou's,
,& yeah i like the steel ruler,& a scribed mark across the wheels for intial setup,& of course measure the distance the flywheels are apart,
with two stroke cranks if factory alignment/endfloat adjustment shims are present,i tend to delete,the tradeoffs giving the big end more "oil" clearance ,i'm talking 10-20 thou at the most, (ossa's mainly), works for me,