I have a 493 with Eddy heads and a Holley SD in my 69 GTX with the air grabber. No clearance problem. You will even have room for a 1/2 to 1 inch wood spacer to keep your fuel from boiling.
The SD performs VERY well. 3.73 gear 3900lbs runs 10.80 on pump gas full exhaust on Hoosier drag radials.