Well, on our gas 350, we run 14/42 with pro-wedges, leave in second and end in 5th, and last race I was running consistant 4.40s with a 4.33. Now, I can't tell you what would be a very good gear to run since I dont know how strong your motor is plus Ive never ran Razrs, but its from my experiences my best times are turned leaving in 2nd, and ending in 5th. Our stock port banshee I was running a 13/39, I ran a 4.799 but I was having to slip the clutch hard to get it to not bog in 2nd, so next race I'll probaly switch to a 13/41.
So my opinion is to gear to start in second, whatever that gear may be. Find some dirt thats similar to your tracks, and figure out where to start in second.