Our engine mount has four bolts, the trick to that style is to figure tighten it and then use a cross pattern to slowly tighten each corner just like you do when putting on a head. This prevents the engine from becoming uneven and messing up your chain tension.
It takes me just a few minutes to change a gear most of that is spent reaching for the gear rack. It takes practice to do it quickly.
This has brought me to another thought. Just like the driver the mechanic needs to practice and work on their race craft. A weekends race can be won or lost in the garage on Monday a week before the race when making plans.