Look for the code on the id plate of the machine. Go here
http://www.mylincolnelectric.com/Catalog/lecooperatorsmanualsearch.asp
you can probably download the operators manual. Its probably 1342 but 1243 is also possible. Model T fords had an unusual crankshaft and were different but it isn't a model T. If all else fails take out the plugs, have somebody crank it slowly with the hand crank while you hold a finger over the #1 hole. When you feel compression in #1 hold a finger over #2 and #3 whichever you feel compression on next tells the story.
bill