BBC Intake Manifold ID help!

[cottonme173]

Hello all!

I am tearing down my 1977 GMC C25 with a 454. I can not see the block casting numbers to help identify the motor specs. On the manifold though is this information:

GMT2
340218
F21 77

I have found many different pages for identification, but 340218 is not on any of them so far. I would like to replace the manifold (if I really need to, current one is in great condition) with something with better performance and a Holley carb. Street driver, nothing really high performance.

I am wanting to know what ports I have to make sure I get the correct intake. Also, more info on the engine would be great to have!

Please let me know if I need to give any more info to help!

-Rob