I found a very clean ThermoQuad in a 76 Van at a local wrecking yard. Engine is a 318, so my guess is that it is a transplant. I didn't think that the 318 was available with a 4 barrel until 78.
I have a 74 truck with a mild 440, 727 and a Dana 60 with a 4.10 diff. Dual exhaust with headers. The engine rarely sees 4000 rpms except when pulling a grade or merging into traffic. Right now it has a 440 spec AVS that was rebuilt TWICE by a local carb shop, but it still has problems. BOTH are vacuum secondary type carburetors, but my question is: Would the 318 spec T-Quad run too lean or would it perform okay? I know Holley carburetors well, but my experience with the T-Quads are limited.
Thank you.

The answer, probably ok. What number is stamped on the drivers side rear mounting foot?

Might want to swap the jets and metering rods to the bigger 440 ones.

Here is the guide http://www.moparchat.com/forums/showthread.php?p=591862

Why Moparts doesn't have a copy of this guide in the tech section is beyond me.

TQ's are more popular than ever before!

Probably okay with a mild motor, but with any cam, you're probably going to run out of idle transfer slot. Just can't get enough air through those dinky primaries to feed a health motor at idle. BB t-quad has bigger primaries.

Check the vaanth thermoquad guide linked above. If it's a 9000 series carb, I would say skip it and look for a 6000 series thermoquad which are the pre-smog TQ's.

You're welcome Commando1

It will likely be way too lean on your 440. The jetting on both the primaries and 2ndaries and the emulsion bleeds will all likely be way off for your 440. Especially if the the carb is indeed a smogger small block carb. Contact me with the 4 digit part # stamped on the driver rear corner of the base of the carb and the top casting # near the passenger rear of the top. I can tell you how to set up the carb for the 440 engine, David.