I Need some advice on a carbi set up for me MQ swb 350 plz. I currently have a Quadi on it which was fine on the 307 for the 20 mins of drivin time

I was thinking of going an edlebrock carbi which is basically a Quadi copy,refined alittle.
Ive been told to go a Holley 600 Vac secondry. Im confused cos ive heared that the Holleys aren't to good for off road use (is this correct ?)
Or are they ok with a few little mods done to the floats and breather tubes?
I may end up running duel fuel later on but do not intend on going straight gas at all.
I have got a few prices for ya info,Holley 600 $350 (Remanufactured)
Edlebrock Carbi $350 to$400 (new) and To rebuild me Quadi $300.
What yas think
All help greatly appreciated
Regards
Jnr