StandardShift.com

Bought a 3 speed manual shifter online. It was supposed to have come from (or fit) an early Ford Falcon. I purchased it to convert my 3 on the tree, '70 Bronco to a floor shift. I believe it will work just fine however, the knob is a left hand thread (it "measures" 5/16" but I count 16 threads? I wonder if it is a metric LH thread?) and I can't seem to find a single 3 speed shifter that has a LH thread knob. I'd like to know what I have. I might like to turn a shift knob on the lathe but I would need to know the thread to find an insert or tap.
Another odd feature is that the shift lever where it attaches to the rest of the assembly takes 3 (vertical) bolts as opposed to the 2 (horizontal) bolts I see on virtually every other shifter. The parts are heavier stamped pieces.

How are you measuring it? There are identification tables based on major diameter (the biggest circumscribed circle). 3/8 UNC is 16 threads per inch and would have a major diameter of .375 and a minor diameter of .3005.

SAE Standard threads are typically expressed as Threads-per-Inch. Metric threads are typically expressed by the length along the axis of the fastener for one revolution of the thread, known as the pitch.

Falcons built in the USA had SAE fasteners in their original equipment.

Most aftermarket equipment for those vehicles would have had SAE fasteners as well.

Falcons were manufactured and sold in oversea markets as well. No telling what fasteners they may have used, especially for later-year production.

A left-hand threaded shifter knob attachment would be an oddity no matter if SAE or Metric.

It may be easier to obtain some nuts with the appropriate thread, thread them onto a bolt with the same thread until they lightly abutt each other, and weld them together. Then bore out the core of a shift knob and epoxy the welded nuts in the bore. You will need an additional nut to serve as a jamb-nut to keep the knob from spinning.

Maybe more importantly, does this shifter fit with your transmission? There may be a set of bosses on the tailhousing of the transmission that the shifter can bolt onto if the bolt patterns match.

Every indication is that it is going to bolt up to my tranny (I have not opened up the tunnel yet but I've seen a number of images of the tranny and other shifters). If not, it looks to be a very simple fix.
Measurements seem a bit bizarre. The bolt measures 5/16 but I count 16 threads/in. 5/16 are supposed to be 18 or 24 threads. 3/8 can have 16.
Confusing further because 16 threads is virtually the same as the metric 1.5 which would be 10mm bolt. The 8mm would be closer to a 5/16 buts it's 1.25 thread is off.
I guess I'll head for the nut/bolt bin at the hardware store and hope to find a matching LH nut and go from there. It's solvable.
I'm just real curious what the shifter did come from and if it ever was on a Falcon or what it was on or intended for.