Thanks for the feedback Eric. Thinking on the shock...

I connected with Millenium Tech. My first contact said they don't repair such cracks anymore. He said they used to weld and plate over, but the cracks would always come back and that was that.

I went back and looked at the website...they have a section called "Unobtanium Cylinder Services" https://www.millennium-tech.net/serviceInfo.php?id=36 that offers repair for irreplaceable parts. Wait a minute- that's what I have. I located the gentleman in charge of that department, Rod Heaton, and he was very helpful. He confirmed he fixes exhaust bridges all the time...in fact he said he has done at least 30 in the last month. He also said, after viewing my photos, he could tidy up the pre-ignition damage in the heads. I'm stoked about all of that- but it's not cheap....and an interesting comparison to the 300 option

Option #1 Repair Existing OEM Cylinders
$ 860 for repair and plate both cylinders and repair cylinder heads @ Millenium includes approx $100 shipping (both ways)
$ 389 for 2 OEM piston sets from Tyga
$ 92 Athena Gasket set from Wemoto
$ 867 Tyga Exhausts
$ 160 2 x shorty cans
$ 112 Tyga Shipping
$ 2480 Total

Option #2: Install Tyga 300 Kit
$1502 Big Bore Kit.
$ 867 Tyga Exhausts
$ 160 2 x shorty cans
$ 142 Shipping
$2671 Total

Difference: about $200.

Reality Check: I probably don't need the Tyga exhausts for Option#1 and instead could use the Ethos ones that came with the bike- but they are very unknown to me- but using them on Option #1 would make it about a grand cheaper.

Hmmmm.