It sounds like you have a Lycoming J series motor in that pumper, they do indeed use Zenith downdraft carbs. Check airplane junkyards, the Lycoming was basically an airplane motor from what I am to understand. It is also dual ignition, 24 spark plugs, 24 plug wires, 2 distributors and 2 sets of points. You really need the orignal motor manual to set the timing or an airplane mechanic LOL
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