For my 78' Grand Prix instead of the standard clamp with the bolt + nuts on the ends. I need to get a little more tilt on the saddle the old clamp can't provide. Found a silver 25.5 post through Harris (QBP online) and when it arrived it had these odd black grooves and looked like it belonged on a toy store bike.

Any suggestions? I'm surprised Nitto does not make an 25.5 seatpost or maybe I/m missing it?

American Classic offers a large range of sizes of their classic (!) seatpost, from 25.0 on up...they can be a little pricey. The Kalloy standard post (that has a LaPrade style tilter/clamp) also comes in a large range and is much cheaper, not the same quality as the AC but does the job.
https://www.biketoolsetc.com/index.cg...d=KY-SP243254S
Biketools etc. has the Kalloy but it's currently out of stock, easy to find elsewhere though.

Can't beat the Kalloy for the money. Seems to be working great on my '81 Grand Prix.