I have a 383 stroker with single plane intake and a Holley 750 dp mech with Dart 200 race ported heads and am @ 490 hp. Am looking to replace the Holley for long cruises. My mechanic is recommending the Edelbrock/Carter AFB but I am not sure whether to go with a smaller 650 carb or stick with a 750.

the 650 will give better throttle responce as well as better mileage with the loss of HP. it should be fine for long crusing.

That is what Edelbrock recomended as well, the new 650 Thunder AVS carb. I think it is based on the Carter AFB but with easier tunability.

Beware. Edelbrock 650's only flow about 500 cfm. Their 650 number is a dry flow number not a wetflow number like a holley. What you may run into is the 650 edelbrock may be super lean on your engine and you may hurt it or have trouble getting it rich enough. If your Vette is an automatic, I would sugges putting a Vacuum Secondary on it of the same cfm rating as the 750 or slightly smaller to improve mileage.

Just bought and installed the 750 mech Performer and I love it. Right out of the box (factory re-man.) it is great even though it is jetted for economy vs performance.