Replace the ignition control with a universal module, but find out what happened to that lennox heat exchanger before you put another one in. I just don't see them that bad unless there is a serious problem
probably don't normally see them that bad because the rollout is usually not bypassed.
Lennox, Carrier, and York commercial heat exchangers come with a 5 to 7 yr warranty. Make sure to check them at about the 7 yr mark. It's almost a sure thing that there will be pin holes starting to form. Check especially at the bottom turn and along the welded seams.