I'd go smaller than the 750's. Edelbrock sells the 500 cfm carb calibrated for dual carb applications so that is what I would use. That gives you a total of 1000 cfm which should work fine with the cross ram.

Mancini or Hughes can sell you the correct linkage kit which is designed for the Edelbrock carbs. Using the Edelbrock carbs saves you a ton of money over trying to find the factory correct parts.