Are Zenith 228s still available in a size to fit a 261? Seems like a 270 GMC version would be close. Those are very adaptable with various venturis and jets.... at least that was true in years gone by. I know they are expensive but we only have so much time left...

1951 3800 1-ton
"Earning its keep from the get-go"
In the DITY Gallery
1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.