Problem solved. The fusable link in the ES300 is the alternator fuse referenced -all my other fuses checked out. I managed to get ahold of the electrical schematics online and starting tracing the failure. Eventually pulled the airbox back out to check power at the starter and figured I'd check the Alternator fuse while in there. Turns out - one of the main buss wires inside the fuse assembly had fallen out of it's location when we pulled the bolts to replace that fuse. Re-attached and all better.