It is very risky, but I have to spend alot of time trying to walk folks through the installation, and have had more than one or two engines suffer due to restrictive engine bays and mostly bad firewall insulation being sucked into the fan...it happens.
Thats one reason I do everything and only build turnkey engines with exhaust,carbs and all in place..there is still a risk that it could be goofed up, as anything can be. The VWs biggest enemy is the wrong mechanic with a 13mm wrench thats for sure, it kills more than junk parts and bad internal labor anyday of the week.
We have very good luck, very,very good luck. In the last 2 years I have installed 3 engines, all the rest have been done by the customer. It seems the guys that take the engine to a local shop for the install have the worst luck, as the shop cares nothing about my engine, or the customers engine and just slap it in.
The main thing is actually letting some jobs go because of being too risky, some people ask way too much of these engines, and the cars they are installed into. One of the biggest things I have had to do is learn how to say NO when the customer has cash in hand, its just not worth it sometimes, I'm sure Kurt knows what I'm talking about.
As for restrictive engine compartments:
I have found that many speedsters need the "Rain tray" cut out and that normally allows enough air into the fan and carbs. Especially for 911 cooled engines.
As for being sued and all that Jazz, my insurance already runs 3,000 bucks a year just on my shop, after July1 of this year that would have increased by 30% if I worked on vehicles and test drove them. I'm classified as an engine manufacturer, and a "Shop keeper's policy" was not cutting it any further. In todays society peple are just waiting to nail you, or nail anyone. To protect myself and my property I had to make decisions and I did so. It did not hurt my feelings though as it cleared up alot of space behind my shop and now the only cars here are mine.
Kurt, Glad to see that you still do install work, I have to turn down alot of work because I don't do installs, and I'll be happy to send those guys your way.