A lot of the timing depends on your ability to spend the $$$. It really boils down to do you want to wait (possibly months) for things to show up or if you want things ready for you when you are ready.
It took 3 months to get a custom panel from SteinAir and 6 months to get the engine from Lycoming.
As far as sitting around the engine will be fine, it's packed well from the factory for long term storage. The avionics risk is just simply will a new, improved version come out while yours is collecting dust waiting to be installed.
Also, don't underestimate how long the firewall forward and avionics will take .. two of us working many hours every day it took 4 months after the fuse was finished to complete the build. I expected weeks, it took months.
They aren't kidding when they say 99% done, 99% to go .. truth!