As you all know, none of our cars have functional cowl drains after nearly fifty years. No one makes them.
If you have never seen a cowl drain, they should be located behind the splash guard behind the front wheel. You just need to unbolt the splash shield.
I had an engineer make a drawing of a modern cowl drain for the 58-60 Thunderbird. It does not look like original, but it should work better than the original. It will be made out of modern rubber, so it will last for decades.
The original duckbill design is prone to closing permanently if exposed to heat and is not exposed to water occasionally. This probably accounts for many of them ending up in the bottom of the fender. They close up, then when finally the old car is washed, it is pushed out of the hole.
This PDF drawing is being submitted for a quote. It may have a split-closed tube at the drain end instead of a open-tube, but the dimensions will remain the same. Measurements are in inches.
I need your help. Please look on you cars to see if this will fit with no interference. I measured the cowl drain hole as 2 1/8 inch. Please verify this. I have pneumonia and am unable to get to my Squarebirds. (I still have low-grade fever and weakness, but am slowly getting better.)
Please keep this design to yourselves. Please do not redistribute it. I will remove it from the site tomorrow night, so print it out now.