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 The stock 965 bases 3.3 turbo engine is fine as a "drop in" replacement but  for the money spent you could build a better 3.6 turbo engine. A stock 3.6 will need as a minimum,  lower compression pistons,  rods reconditioned with aftermarket rod bolts, turbo scavenge pump, aftermarket fuel injection with bigger injectors, intercooler and turbo/exhaust system. This engine has the potential to make 450-500hp  The stock 3.3 965 turbo is rated at 330hp (?)  The suggested limit on the CIS injected turbo engines is 400-450HP.   Starting with a 3.6 gives you more upside unless you can find a  inexpensive used 3.3 turbo.   The weak point for both engines is the cylinder to head junction. The 3.6 head does not lend itself to the Ni-resist modification as well as the early 3.0-3.3 cylinder head.  Randy Aase has developed a "stepped" Ni-resist modification that can be used successively and some people weld up the side of the head with this modification, but I feel the earlier head is still a stronger configuration |