It can be done with the engine in the car, normally it's done when you have to take out the engine for another reason.
Most of the sets I had fabricated were sold to owners and garages who serviced the car and had the engine out.
Even if the mounts are bad you can drive, on my car the gear shifting became hard because the angle to the gearbox wasn't aligned any more.

I replaced mine after we went to Italy 2003 with both my cars, that was the time when I had these stronger ones made.

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RaymondQV
Countach QV Ex-Mimran #GLA12997, Urraco P300 #20530 sold in August 2008, Jalpa #FLA12203 sold in May 2006
www.countach.ch
www.jalpa.ch

When Frank Sinatra got his Miura S in 1970, he said: “If you wanna be someone, buy Ferrari - If you are someone, you own a Lamborghini”.