Autolite to other brands

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I have a commerical air compressor that has a V8 engine[Ford I think] with four sparkplugs on one side and an air manifold on the other side.It has autolite # 26 sparkplugs in it.How do I cross reference these to other makes,[such as AC or Champpion or NKG, etc].The rig has been sitting outdoors for a few years,It starts and runs at high RPM with the choke par out part way but stalls when it idles down under load as the pressure builds up.I think it needs a tune up.