Well I found that the "standard" Fiat splines were 20 and 38. Then, if you read that thread I gave a link to, you'll know that Joe Webb found his 37-spline column was from a Cinquecento.
Guess what? According to stuff I've found on a Fiat 500 forum, some 500Ls were also supplied with a Cinquecento column, only this time with 21 splines. So looks like you may have a Cinq column too!
Seems Fiat were devils at fitting any old thing to the production line. Mind you, during one of my jobs in the motor industry I heard the same thing about Ford regarding headlamps - if they ran out of the specified headlamps, it was cheaper to fit any old rubbish (typically last year's now-obsolete sealed beam units...) and sort out any subsequent warranty claims if a customer ever noticed, than it was to stop the production line while they waited for new stock of the right item to arrive. And that was from a design engineer at Ford Dunton in Essex, so I'm guessing he would know!
Reading around Bar Vitelli's thread today about the Otto Bulloni I found this information from Coy's auction house:
<< In 1965 the Nuova 500 F was introduced as heir to the “Dâ€. The modifications were mostly aesthetic, the most obvious being the removal of the so called “suicide†doors: in 1965 the law was changed in Italy forbidding the manufacturing of cars with door hinges on the rear of the door. The body was also modified in many more ways than meets eye. In reality all that maintained from the “D†was the bonnet and the front of the car. The tank was now larger, its capacity increased to 22 litres, the engine had revised valve timing and delivered 18 hp, the suspension was stiffened and the axle shafts of greater diameter. Even the braking system was enhanced and used bigger brake cylinders. Initially the 500 F used some pieces of the old D, waiting for the introduction of the new parts and also exhausting old stocks of Fiat (which was quite common at the time).
The car we offer here today is a part of that small batch of cars, which are known as the pre F, built from March 1965 to July 1965, this series is different from the latter due to the concealed door hinges that are fixed to the body with 8 bolts. Other important fine details are door handles and window winders constructed of cast aluminium instead of the plastic that was used later, the seats are derived from the D version with supporting rubber bands, headlight rims, front wheels, the support of the front indicators, the grille and hub caps are all aluminium as on the previous version D, and from May 1965 they were being replaced by cheaper material.>>
Obviously Fiat were into mix 'n' match long before Woollies thought of the term!