New oil pressure switch doesn’t fit...318 LA

3/8-24 is quite close to 1/8 pipe. The reason I know this, is that "in a previous life, I DIY built loading coils for a multi band HF amateur radio mobile antenna. This consisted of about 4' of 1/2 water pipe coming up from a DIY hitch receiver below the bumper, with an insulator at the base. This 4' was the bottom section of the antenna

At the top of that, I built various loading coils for each amateur band, 3.8mhz, 7.2 mhz, 14.2 mhz, and 21.3 mhz. And just used a pipe coupler and no loading coil to couple to the whip, which was a broken off CB whip. This resulted in about 8' (?) or so for the amateur 10 meter band at 28mhz.

ANYway, the loading coils were various PVC fittings and couplings or pipe glued together, with a steel pipe bushing in the top for the whip to screw onto. This was a larger size down to 1/8 NPT, into which I "chased" clear through with a 3/8-24 as that was the whip thread. You don't need to drill it, just run the tap through there. When you get done, a 3/8 NF bolt goes right in, all the way through