I've noticed there are several of the 3" oil/steering coolers which have 1/2" npt fittings, and Rex has the 3" with 3/4" npt.
CP has a 2" coooler with 3/4" npt.

Which would run cooler or more efficiently? If everything else is plumbed for 3/4 npt to -12an, isn't it kind of silly to use the 3" with 1/2" npt?

I am trying to get my oil system down for my 496 stroker/Gen IV. Not sure I need a 3" cooler - it's kind of big for my stringer mount location.

Thanks

If you do any extended running you need the 3". I cooked an engine last year due to a small cooler. I've actually had trouble with a few rebuilds and finally tracked it to excessive oil temps. Plumb a gauge into your pan and you will see.

You probably will notice little difference between the 1/2" and the 3/4". If you do, than you probably need a bigger cooler to start with. Needless to say, bigger is better. If you have a choice buy the 3/4" as its ID is almost the same as the -12 line,(about .66 ID) where 1/2" npt is .1 smaller(about .55 ID) than the -12 line.

If you use the 1/2 npt size cooler, use 1/2 npt to -10 AN fittings and -10 hose. They have quite a bit larger inside dia.

Go with the 3/4" pipe and -12 AN fittings and hose.

Run an oil temp gauge. Peroid. It costs way less and is alot easier than replacing and paying for another motor.
Buy a cooler that is rated for more HP than you are making. Make sure there no major restrictions in the water flow, and make sure the oil cross-flows against the incoming water supply in the cooler. BBB