Should I do a Cat delete on '75 Duster

Removing the catalytic converter and doing nothing else won’t add much, if any, horsepower.

Now, if you undo the other smog year changes- timing, compression, carb, etc AND remove the catalytic converter, you’d get some performance back. Nowhere near 50 hp though.

If you’re doing an engine swap, just drive it as is until then unless the catalytic converter is plugged up.