What rear end are you running? 2200 RPM at 70 MPH is why you need to downshift on an incline.
With all of that carburetion, you need to spool up the RPM to realize any gain with that setup on a 235.
Not saying that you may not have another issue going on, but a setup which gives you 2200 RPM at 70 MPH is not a great starting point.
