Is this the kind of information your looking for? If your willing to spend ten bucks then this site may be able to help you out with a handbook:
Author(s): Howard Rotavator Co., Inc; Title: Howard Model J: For Cat. I 3-Point Hitch Tractors 12-28 Pto H.P. Owner's Handbook & Parts List, Fourth Edition; Illustrated; Publisher: Howard Rotavator Co., Harvard, Il., 1977, 4th, Trade Paperback, pp32; Condition: G In Wraps. Worn & Soiled, Stained At Rear. Ink Notations On Upper Front Cover. Keyword(s): Tractors, Automotive. Item Number: I60020 Price: $10.00
Ford N newsletter people that keep photocopies of all this manner of thing. They have the owners manual and parts book for the model J. Look under Plows on the link below - scroll down to the last entry and it will read:
___ Howard Rotavator Model J OM,PB (36)
They have instructions on the page for ordering.
You can find them at:
<A target="_blank" HREF=http://www.n-news.com/archives.html>http://www.n-news.com/archives.html</A>
All the best with it. My father used a Howard back in the 50s and thought it to be excellent. I just have a little LandPride on my BX.