I believe the Mofoco heads are ok these days.
I have Mofoco’s on my VW, Scott Casler’s been using the Mofoco’s forever on his Hummel engines.
If I recall correctly (from the VW forums) Mofoco had some quality issues a number of years ago when they were changing casting vendors.
A lot of unhappy VW customers at the time. That has apparently been resolved now.
CB’s are probably known to be the better quality but as I understand CB has been blacklisting people using their products for aviation use.
Here’s a thread on the subject
http://vwaircraftengines.com/viewtopic.php?f=25&t=311Not sure if that has anything to do with this change in supplier in case of the AeroVee.