David C - I still haven't decided what I might want to do, may just do the seal.
Frank - my bet guess on the ACE oil would be Pennzoil since that appears to be the only other brand they sell. Now, about the tail light bases, those numbers sound correct, but I'm afraid to remove my lenses to verify since the dang things tend to crack with age. Did you find that 85.5 belt? There aren't as many 50 decks around.
Glen C - wasn't long ago someone on here had very similar symptoms as yours. He ended up figuring out his condensor was wired to the wrong side of the coil. I still say you gotta check and set your timing with a timing light. You didn't say if you increased or decreased your point gap to get to .018 but you could try going just a little more in the same direction to see if it improves more. Could be your little points push rod has flattened out and needs replacing. You also need to make sure your governor is set correctly. Maybe the clamp on the rod has slipped just slightly and you're not getting full governor control.
Melody - ole Charlie is probably cutting ZZZZZ's right now, but if you're lucky he might just pipe in and tell you some differences in the tillers. About the only thing I can tell you is the Model 1 and 1A are listed together in the CPE-2 Parts Catalog and it states the Model 1 was built 1966-71 and the 1A built 1971-74. All the parts for these 2 models are listed together except the right angle gear box. It shows the Model 1 gets the gear box that has 3 mounting tabs for bolting it to the mounting bracket, and the box itself has that die cast cover with the fill plug. The Model 1A has the gear box with 4 mounting tabs and the box that has the IH stamped cover with no fill plug. The other parts internal to the gear box all seem to be the same. They both show they use the same 30 tooth and 20 tooth gears, giving you a 3:2 ratio.
Then there is another section for the Model 2 and 2B tillers listing them together and showing most all the parts being all the same. The Model 2 is noted as being built from 1974-80 and the 2B from 1980-Since (to the end of IH I guess). It's intersting the right angle gear box for the 2 and 2B has all the same parts as the Model 1A gear box. Then when you get to the other parts of the tillers there are a couple areas where they show the belt pulley being different between a Model 2 and 2B depending on the drive belt being used from the PTO on the tractor, but other than that the 2 and 2B are basically identical.
Hope this helps you. Best I can say from this is if you are looking at a tiller with a 3 tab mount gear box it's a Model 1, and if the gear box is a 4 tab mount it could be a Model 1A, 2 or 2B. You could try looking at the pics of the housing and chain guard in the Cub Cadet parts lookup link above. I think the 1 and 1A have some differences in appearance from the 2 and 2B.
(Under Edit - I just looked at the parts look up and they really don't provide you pictures of the 1 and 1A, and those of the Model 2 don't really show well).
