Well, my experience conflicts with what has been indicated so far. I had one of those cheap chrome stamped steel covers on my TH400 and was looking to upgrade to a nice thick polished aluminum cover. The only one I could find at the time, about a year ago, was one for a TH350, well the salesman said "no problem, it will fit a 400".....wrong! The covers were the same size alright but I had to drill and tap new hole in the upr R/H corner of the trans and enlarge the slot on the cover for the upr L/H hole. Now, it would have been easy for the manufacturer to make this cover to fit both trannys but such was not the case and I ended up modifying both the cover and the trans to make it fit. Anyway, thats been my experience. By the way, that's a heck of a good price on those E-bay aluminum covers, I think I paid close to $80.00.