I agree. Without a cam change and cylinder head work about all you can do is some improvements around the edges, so to speak. You can add a different intake manifold which is some help, but the selection of intakes that will fit under a stock C3 hood are limited. An Edelbrock Performer is one of the few that fits and will help, but you won't see a huge improvement.
Having your Q-jet rebuilt by someone who knows them will be a help. Adding electronic ignition will help starting but won't be a huge improvement either...it mostly reduces maintenance but doesn't help much in and of itself.
Adding exhaust headers can make a noticeable difference, but selection is important to get the right set that does what you want.
Do all of those and you can notice a distinct difference, but still...it will require more serious work to see a substantial increase in performance.
I had a '78 L82...I added the Edelbrock Performer intake, had the Q-jet rebuilt, and kept the stock exhaust manifolds, eliminated the catalytic converter and installed a true dual exhaust (which a '74 should still have)...it made a nice difference. Not so much stump pulling torque but a it was really a nice, reasonably power engine that did everything I wanted.