Would you still run-in a rebuilt engine though, as opposed to a new car?
It is an awful long time since I did an engine rebuild. Last fatal engine problem was in 1990's, and got engine replacement under warranty. I know a lot of folk buy replacement short engine rather than take on a rebuild.
Guess I have to go back to 1970's, when last I did a complete rebuild.
These days, I do not see the myriad of specialist workshops that were there to support the engine rebuilder. Guess these days they maybe can be found on line.