Sounds like you are on the right track.

With carbyied engines this would be my order of investigation.

Simple things first.

Spark...Disconnect one each of the spark leads in turn, holding them with insulated pliers and check for arc to earth. This tells us we are getting spark to each plug.

If the plugs or leads are questionable.. replace them!

Check Distributor...Ensure gap is correct. Ensure points are in good condition. Wipe out the cap with a clean rag if there's any condensation.

Coil Voltage (check for broken dropping resistor)..Put a voltmeter across coil. During crank you should get 13.8v, when sitting an IGN position, it should be less (~9-12v)

Petrol...disconnect the coil, and crank the engine for 10 seconds. Remove the plugs and see that they are wet with petrol...Put the plugs back in. If they aren't wet with petrol, then look at fuel filters and fuel pump. Disconnect the fuel line to the carby and have someone hold the hose into a tin while you crank it over.

Check you've not blown a head gasket, radiator water should be either coolant coloured, or rusty water . It shouldn't look like a rusty or lime milkshake.

The engine should be flooded at this point. Foot flat to the floor and crank it over.

If the engine doesn't start, have a smell around the carby. If it's particularly fumey with petrol smells (more than normal) then maybe the float level in the carbs is too high.

By putting your foot flat to the floor, you are also bypassing the idle jets in the carby, in case they are blocked. Thus explaining why it doesn't start normally.

These principals can also be used to fix your lawn mower :) :) :)

Chris