John,

Nice looking project. Was it tan before ?

Since this thread has evolved from the subject of vacuum to oil cooler lines...

I would not recommend plugging off the oil cooler lines(stubs) unless you remove the filter housing from the block and remove the oil cooler thermostat and spring. Otherwise, if your oil does ever reach 95c and up, the thermostat will start to block off much of the direct flow to the filter and open the line to the cooler, which will now be blocked off. Oil will still get by, but I visually estimate the restriction at about 80 to 90% . The therm. is easy to remove and is the safest way to go IMHO.
Brad.

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Diesel-guy