Despite the fact that Holley says that is a 1000 cfm carb, it really isn't that big. Due to the preponderance of aftermarket companies making questionable claims about the cfm ratings of their carbs, Holley joined that game a long time ago, and for a lot of their carbs the cfm ratings are way optimistic. A good example is their 950 carb. This carb uses an 850 Holley base plate, and a 750 Holley carb body. Real cfm is clearly somewhere in the 800 cfm range, but Holley calls it a 950.
Their "1000" cfm carbs are 850 carbs that have smoothed over airflow openings and no choke, plus some other features. As a guess I would say that they might be as much as 900 cfm, but probably not more than that.
The carb numbers that I know you can trust for cfm from Holley are the 600 to 850 double pumper carbs, and the 750 and 780 vacuum carbs.
A 482" engine is a pretty big one, which is why I suggested a big carb. More info though would be helpful, particularly how much RPM do you plan to run, and how much horsepower does the engine make. Did you get it dynoed at Survival? By the way, Barry at Survival knows more about carbs than most folks; did he make a recommendation? Since he built the motor, his recommendation would be the best one.
In general, you should run the biggest carb that you can to make the most horsepower; the tradeoff can be throttle response and fuel consumption. For what it's worth, I ran a 750 double pumper on a 450 HP 428CJ for many years on the street, and that combination had excellent throttle response and didn't give up much, if any, top end horsepower. You have about 12% more cubic inches, and probably 100+ more horsepower. Factor that into your decision. I wouldn't go any less than a real 850 cfm.
I doubt that you will need to beef up the front suspension; you might need stiffer front springs, but I'd try it with the springs you've got before making any changes. And I would just recommend adapting some stock FE mounts, maybe from a late '60s Mustang, and use a torque strap to limit movement of the engine.
I don't know Arron Johnson; maybe someone else here does...