Re: carb size???
Intended use of the motor can have a lot to do with carb selection. How you drive or prefer to drive can play in. Trans type, gearing, heads can also play in. A 750 DP holley can feed a lot of motor but there is a growing number of guys that are stepping over the ageless 850 and going with the 950 HP (which the stock Holley 80496 does NOT flow 950 but rather a little over 800. The 850s are pigs and that huge 1 9/16th venturi size on a 1 3/4 base makes it not real street friendly down low. Cruise/part throttle jitters have been a complaint.
Give us a little more info on the big picture. 525 is a lot of street horsepower. The track can require a totally different setup. Good luck with that Holley carb selector. I hate it. It has told me more times than not that they do not have a carb for me base on the information entered which is a joke. It's also a very rough "get you in the ballpark" tool.