Base clear doesn't sound like it would work to me. If the texture is different it will look funny. I see cars in traffic that have had doors and fenders repainted and the difference in orange peel next to the nearest oem painted part gives it away even if the color is "close enough".

PPG Delstar acrylic enamel is likely as close as you can get to the factory paint. The color won't match so you'll have to have it tinted/adjusted for the cars age, newer paint ingredients, etc.

Seems like using the top quarter panel edge over to the Dutchman panel seam and then to the bottom of the roof would be less noticeable? Carefully back-masking on the edge of the quarter and the Dutchman seam would make for no tape lines. Where to stop at the roof is the tricky part.