Ok, history: the PCV was made mandatory in '68. Until then most didn't. They used a simple valve cover breather, the Chevy tube with cap in the front of the motor was very common, the older Y block Ford had a pipe hanging down slant cut to help the vapor escape.
In strict engine terms, a PCV isn't necessary at all. What is necessary is some way to let crankcase vapors out - even a motor with 5% leak down means it's pumping 5% of the CID out past the rings. The racing Shelbys used a tall tube and cap on each valve cover to get it out.
A PCV is for emissions - it's a spring loaded valve that allows the vapor to escape thru the induction system, set up properly, it won't vacuum the crankcase at all. At high flow rates some close off, and if blowby is really bad, it still pressurizes the crankcase.
Since most laws are predicated on the statuatory age of the motor, with the engine year being the most significant, if it's a post '68 block, it will have a PCV. Titling it as a '65 may not help if that state lays claim to the later engine requiring all it's emissions devices. That should be cleared up first before making a decision.
Most crate motor builders don't have a PCV in the system simply because they have no idea whether you are using it for race or street. "They left it off." means nothing about whether you need it. Not all motors use one, either, some use the CCV system, which is nothing more than a small orifice left open and plumbed to the intake. With that arrangement, the valve cover breathing is routed back to the air cleaner and if high pressures are encountered, the vapor passes thru the filter into the motor.
On worn motors, it dumps a lot of
oil on the filter, which the factory cares less about. Science it out which way you are required to go, if necessary, then choose one. If you do choose to go for an active system to keep crankcase pressures low, expect expense out of proportion to the few hp freed up at high rpms. It's another race part that almost never pays its way on the street.
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