Double plumper carb or stay with Vac sec carb?
I've made vacuum secondary carbs work well in your situation, it just took time & tinkering to get there.....Looks like a 750HP would be the most cost effective carb for a upgrade?
If you really want to make some hey at the racetrack, do the carb, the gears, the M1, and talk to a good converter builder to build you a nice 9.5" that will give you some serious 60' capability and still be streetable on a limited around town basis...