Hello Glenn,
Very sharp tractor! I noticed the filters and didnt think those were right. I'm sure you already know this, but on those 201 diesels, the two filters on the outside were your primary and secondary stage filters and the one on the back of the block was your final stage filter. Had to replace the final stage filter only 33D because it had a pin hole in it, which is why I also thought it didnt run right cause it was suckin air.
As for the production numbers of the 333D, I dont know either and have wondered that myself. I'm sure someone else on here would know.