Not their street slayer series vacuum secondary carbs. Quick Fuel, just like Holley, have different versions of carbs from mild street to wild race carbs.
You'll have to use an adapter to bolt the Thermoquad up to your intake because the TQ is a spreadbore carb and your intake is made for square bore carbs only. If you don't mind doing that and you have a Thermoquad that your sure is rebuildable and your capable or know someone capable of rebuilding it might be a good choice. In the end you can do as you please but for a 385 horse engine I wouldn't use anything less than a 700 cfm carb. Your just giving up horsepower you paid for if you do. Why did you use 5200 rpm as the rpm limit in the calculator? I'd be really surprised if your 360 made it's peak of 384 hp at that low rpm.
One thing to keep in mind about most carb calculators is they don't take into account for the space fuel takes up in the airstream so they generally predict the size quite low. Wish I could remember the formula for the space the fuel takes up at a WOT ratio of 12.8~13 to 1 where you generally make the best power it but at the moment it escapes me but I remember using Holley's calculator and it said my 450 hp 408 only needed a 697 cfm. I know for a fact by testing that it runs much better with a 850 vs. a 750. That proves the calculators aren't always accurate due to the restriction fuel presents in the venturi's.
One last thing, why are you second guessing the professionals that built the engine? Seems to me they'd know what worked on it the best. As for their recommendation of a 780 being too much for a daily driver. Too much in what way? I've seen guys run dual 1050 dominators on a tunnel ram on the street and they performed fine. You have to remember that a carb doesn't magically force it's max cfm down the engines throat, the engine draws what it needs in conjunction with how far you press your right foot down. Can you over carb your engine, sure! Is a 780 too big, no way!