Check the low-tension wires and connections. Especially the little braided wires inside the distributor. (You can buy this wire from a well-stocked auto electrician).
Check the rotor button. A 4 cylinder one will fit perfectly but the engine will not run well at all and certainly will not rev.
Replace spark plugs
Check the fuel. Especially for old stale petrol or build up of deposits in the carby.
Check the timing. Don’t move the distributor out as there are 13 positions for the drive shaft and only one is correct. It is a "dog of a job" if you don’t have the sump off.
Do a compression test to see how the valves are sealing.
Sometimes if an engine has not been run for a long time it will benefit from being allowed to run for an hour or so – gives it a chance to rediscover its usefulness.
Check that the slow running jet is still in place in the carby.