Testarossa Door strakes screws help

MPC shows it as available:

https://www.ferrariparts.co.uk/part/search?SearchText=20286704

or did you try them, and they said it isn't? (Although agree it's just a "normal"-sized metric pan head screw that should be easy to get elsewhere.)

 

when it is metric size then in europe it is no probolem to find. even every hardware store has them. may be not in black but galvanized for sure

your personal info says you are from MO, so is this modena in italy or missouri in the US? may be in the US it is not so easy to find metric screws? then you may go to a european car shop, they for sure have.

 

the thread looks like M6 or M5. it looks like standard pitch. so when you order M6 it is 1,0 and when you order M5 it is 0,8. from the photo at steve´s link I would say it is M6. take a caliper please and meassure the outside diameter from the thread, then you know what you need. and the length you may meassure the lenght of the blind holes in the side strakes, add the thickness of a washer, then 1 mm for the doormetal and subtract 2 mm, better 3 mm then you have the length you need.
best is to take 1 side strake and just test if the screw will fit. I never took those away so I not know what size they have

 

https://www.ebay.com/itm/234463554452

looks different than the pic fparts uk has

 

And this one - https://www.ferrariparts.co.uk/part/ferrari/13274411

which is a supersession of this one - https://www.ferrariparts.co.uk/part/ferrari/13274472

looks like a longer version of this one - https://www.ferrariparts.co.uk/part/ferrari/20286704

 

I have FOUR Testarossa's and there are THREE different mounting configurations for the side strakes depending on year.
!991 and 1990 use a small stud and acorn nut on the top mount. The lower bolt is a metric machine bolt that uses an 8mm socket. I'm going to say these are 5mm bolts These appear to be secured with NUTS on the inside of the door. 1989 Testarossa uses TWO 4 millimeter phillips head machine screws with mating brass nuts on the inside of the door that are seven millimeters across the flat 1986 Strakes are held on with a LOT of bolts- two each- i didn't count.

What YEAR is your car. I have an 89 parts car with door panels out- so easily ascertained what it uses. Most people are NOT going to remove their door panels to answer your question. there's NOTHING special about these fasteners The one I took out of my parts car might be 5/8ths inches long- long enough to go through the outside strake mount, the door and room for a nut. Probably had a black oxide head at some point. The strakes on the later cars are also held on with a 6mm socket head cap screw at the top of the strakes. They're an assembly on the late cars and separate on early cars.

The little black oxide acorn nut used on the top mount of the 90 and 91 may be challenging. I didn't stick a socket on it, but I'd bet it would be a seven millimeter across the flats- smaller than the lower bolts.

 

I had a micrometer AND the removed phillips machine screw for the 89 sitting in front of me. It's a half inch long and .151 in diameter- a few thousanths under 4MM. You could just use #8 machine screws at .161 diameter. I think the interior BRASS nut is a good idea, as it's a wet location and the nuts are not in the clear. They're both behind a bracket or window part- so if they rust up, you'll have fun getting them out. Yeah for Ferrari for using brass.