Yes, deffinately read Edelbrock's literature on Carb tuning.

I have a 400 (402 actual) punched to 410ci. I'm running the 1406, basically your carb only with electric choke (our engines basically have interchangeable parts with the exception that I'm running 2V heads). Since 400's are made for low down torque and lower RPM's, a 750 would just suck more gas and give little in return.

Did you buy the calibration kit for your 1405? If you haven't, do. If you have, buy some additional metering rods. I found the kit a little lacking and purchased 3 more sets of rods for extra fine tuning. Good luck!