The pipe diameter is unlikely your issue. Pipe diameter only really matters at high RPM. On the street if you are not winding the snot out of it you will never know the difference. What can be noticeable at lower RPM is header design (tube length, tube diameter, collector length).
What carb is it? A few knowledgeable people here will say a 4 barrel on a slant is a track only carb. It is a struggle to get drivability out of it because it’s hard to find a small enough carb to not flood it with too much air in normal driving conditions and getting tip in bogs and hesitations. I can not confirm as it have dual one barrels and have not tried a 4 barrel on a slant
