It will cost you the same to rebuild the 326 with HO heads than a 400.
Buy a good 400 core with as much bracketry and as complete as possible, most from your 326 will work.
The replacement pistons available for a 326 are usually cast and not forged unless you have custom Diamond or Ross made. If you rebuild, get a complete kit from Summitt or Jegs instead of piecing it together.
I used to rebuild Pontiacs at a shop, so IMHO, I say go the 400 route. I can help locate a core for you as I am 15 minutes from Windsor and have many sources.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
