New Carb Recommendation

If you unplug your vacuum advance and go past 16 deg it won't start?

You could go with a MSD box with start retard. It retards the timing 20 deg until the engine breaks 500rpm.

FTR, I'm not a fan of vacuum advance on a performance build. I like straight timing.

I agree with cuda. the quickfuel or a HP series carb will suit you well. I run a 950 proform and have had great luck with mine but would not recommend taking that gamble. I've heard too much about production quality issues. Stay away from demon.

I'm not sure which XE274 cam you have (they make 5). YOu may benefit from a little more convertor. I'd get it on a chassis dyno and see where your peak torque is being made. If it's over 2600, I'd do yourself a favor and make the call to PTC, dynamic or the like. What brand convertor are you running right now? Is it a custom or an off the shelf unit. That could be part of your problem.