273 Commando with Hydraulic Camshaft

Have you tried tuning the distributor curve and carb to get the most of what you got.
Engine looks fairly stock unlikely the person put a way too huge of a cam in it, you might be expecting to much from the little 273.
I tried to figure out what you have now, no point swapping cams only to pick something that's similar to what you got now, If you looking for bang for buck and don't mind deep gears go 3.91 plus, 3.23 might be ok behind 360 plus engines but are pretty high for a 273.