Just read about this company which makes a XJ13 replica (unfortunately not within my budget, would love to have one of these).

They made a DOHC V12, and sell this one also separately

https://buildingthelegend.co.uk/introducing-the-tera

Startup of the engine:

I can't find any video's yet where its racing, but I found another great one to listen to, the sound there is already beautiful, turn up the volume from 03:09 ;-)