Information on tractor changes

Hello all, started off collecting Farmall's in the early 90's, sold them, went to John Deere's, sold them, and now back into the Farmall's again. I just like old tractors! My question is, where can I find information on part/design changes, specifically for the Farmall H and M. Part of the fun for me is having (looking) for the correct piece/part for the particular model or year. For the Deere's, there was a book called " The Unstyled A, a specialized look". The author (who I know) went to Deere in the years past and copied the archive changes - back when you we allowed to - and recorded many parts changes down to the serial number in most cases. I noticed some changes that were missed in the first edition but were added in the subsequent updated editions which I had mentioned to the author. So, like the Deere's, I would enjoy finding out what part generally belongs on whatever year of the H or M. I know sometimes there was no rhyme or reason why whatever was used same - with the Deere's. From what I've seen and researched, there is no "book" or website that explains when parts where improved or updated. Things like pto covers, throttle speeds - sawthooth vs notch, seats, hoods (some have more holes than others) drawbar parts and all the other stuff. Thanks all for any direction.

The author has been on the site in the past. 8 years or so ago. Wealth of content. Jim
Letter Series Farmalls

Thanks Jim. I actually have this book - but I loaned it to a friend several months ago. I'll have to get it back and see what it says - again.

But that big Red book, lacks a lot of details, that i think you are looking for,not sure where to send you to look, a good late parts book list a lot of the changes with part number's and such!

That's what I was thinking FastFarmall, the guide book is just not detailed enough for me from what I remember. A parts manual would be the way to go in my case. Thank you.

Absent all the information IH compiled about changes the next best thing for some models is to find the earliest and others through last printed parts book for the model information is wanted for. Still won't tell you why the changes were made or exactly unless a serial number is listed with a change. Some bulletins IH sent out still surviving have a reason for a change. Also some information through the Wisconsin historical society.

The one thing about IH was they kept track of part revisions by the part number suffix. Say a part number 6225D changed, first revision was DA, second change DB, third was DC. Or a part number 356491 R1 was first release, R2 was first revision, same with 356491R91 assembly first release, R92 was first revision. Parts with the same part number, not the suffix was both forward and backward compatible and interchangeable.

Now, what would be harder to track would be a change of part number. Part numbers could be changed, advanced several times with parts being interchangable.

The saw tooth throttles for H&M and the change to square tooth throttles with the replacable tooth for the throttle lever was more of a product improvement part or package. Very different part numbers, different routings, different machines, it obsoleted the saw tooth entirely. There were notes on the prints for the new parts explaining the change, but you probably would never be able to get your hands on those.
I started working at Farmall about 4 months after graduating from college, worked my way up from an hourly production worker to salaried material control person. I had relatively free access to prints, I've read several articles and even books on designing a proper part numbering system, and IH's was perfect until they had to start using seven digit part numbers. A six digit number was always pronounced as two groups of 3 numbers, seven digits were pronounced as a single digit, then two groups of 3 by some people, others said two groups of two, then a group of three by others. Some people just used the last three digits, but there could be parts with the same last 3 digits, one with 6 digits, the other with seven, BIG confusion!

Thanks for even more info Dr. Evil.

I have t his book, found another copy on the City Library Discard table for $1. Could not pass it up.