I don't think you will loose power by going to two TBI on a stock type M.W. intake and heads, on a set of stock port size 440 heads with the same type and proper size intake port manifold, maybe you will
The tuning might be challenging though
I've race and driven several different stock type M.W. motors in several different cars, they where all faster than any single carb car out there back in the day, prior to 2000 More air and fuel, more power