Don't rule out the basics before throwing more parts at it, get rid of old fuel, put fresh in.

Check the compressions. You say it's got a recon head, how long ago?

I recently faffed around for a couple of days on a car, all it had was contaminated fuel that kept fouling the plugs. New plugs and fresh petrol, away it went

Other thing is, if you say you have one of those see-through dizzy caps and see no spark on 2/3, have you tried another cap?