I finally found a suitable substitute for the Clark air cleaner. I have been looking for vintage tractor air cleaners on ebay. Quite a few show up and most do not fit the measurements that Bill posted above.
The ones which most closely match come from Case, Farmall and Minneapolis Moline tractors. The problem is that all the ebay sellers do not post any dimensions and it takes a few emails, calls and patience to find a good match. here is what I purchased for $20 after a 2-month search:
Minneapolis Moline 445 Air Cleaner Assembly 335 Jet Star 4 Star. All of the measurements are nearly exact to Bill's with the exception of the intake and output pipes. They are both 1 3/4". I think i can make that work. The other consideration is the mounting bracket on this one is sweated on. The "growth" on the upper pipe is a piece of rubber tubing inserted on the top.
I also found a suitable match for the mounting rings. There are: P04055 DONALDSON AIR CLEANER BRACKET and run $19. The dimensions are nearly perfect. The only difference that I can see is that the bracket to band attachments are spot welded with 2 tacks instead of 4 on the original.