"D" Zippers Intake Manifold vs. "O" Mated to "D" Intake

[geezerglide]

Just replaced the stock TB with a Zippers 50MM TB on my 04SEEG, when they pulled the old intake it was the "D" shape to match the head that SBC did which I had forgotten about, (getting old). Well we had no other intake so we used the Zippers "O" mated to the "D" intake ports.

My question is, what if any effect will this have with performance?

Thanks,

geezerglide

[se]

not much diffrence at all.
i used to run a d manifold for htcc non cnc heads in my build and when i switched to a regular "o" manifold not much to mention.....