Let's start with two old school checks that (1) are well within the ability of most home mechanics and (2) are appropriate for an old school car.
Before you being, pop round to your local major auto parts store that loans tools (actually they don't loan, you buy them and then bring them back for a refund). Assuming you don't own these already, acquire a vacuum gauge and a 3/8"drive torque wrench. Then ask the salesperson for an old-school spark plug gap gauge, the kind that uses different wire thicknesses rather than a flat style or feeler gauges:
For both of these tasks, we'll need someone with good knowledge of the US-spec 1974 1300cc for details denoted by *** to help us out with some details.
First task: pull all four plugs, lay them out on a paper towel, take a pic and post it. While they're out, check the gaps***, adjust if necessary, and re-install to the correct torque spec.***
Plug condition and color can tell us a lot about rich or lean mixture.
Second task: connect the vacuum gauge to manifold vacuum (where?***), start the car, and record the gauge say 15-20 sec with your phone. If you have a helper, it might be interesting to a "cold start" version of this as well.
Vacuum gauge behavior can tell us a lot about valve timing and valve train condition.