273 upgrade to 4bbl?

I agree. AND i think the port mismatch is not as big of an issue as most make it out to be.
The factory put the large port four barrel manifold on the small head 318 engines from 78 up.
It worked OK although not totally optimal.
It is that particular set up on my 318 Stock Eliminator Aspen O/SA Wagon that set the National Record
in the 11s and I would not worry about it very much on a street car.