Never wrong to make sure you can get cam chain on the crank before head is tightened. It should be enough to just lift chain make it to hook onto the crank teeth.
One thing easy to forget when mounting the cylinder is the cam chain slider. But easy to get on by lifting the cylinder just a little to get the steel pin into the slider hole, without dropping it ....
All pistons at same level avoiding any of them to get a ring outside.
I have heads I thought should be used with the longer slider.
But it did not fit, longer slider stopped by too small opening in head . It is a small curved corner on the left that must be filed from beneath, not all the way up needed. Avoid making gasket area for valve cover too narrow
The shorter slider has thin rattling pins sitting in cylinder top. Longer has thicker sitting tight.