I think probably the Farmall H (1939-53)and the post 1935 Farmall F-20 was farmalls competition for the 70.The M and the F-30 were pretty equal to the old fashioned no thrills model 80.
 
The case CC (1929-1938) and later DC (1939-1952)was case&#039;s slightly larger competitor to the 70. 

Minnieapolis Moline model R I think was molines more modern tractor of the time. It often reminds me in looks to the Oliver Hart Parr 70 grill appearance. You might want to look into the model Z too though. 

Massey Harris had the model 101 and the twin power challenger to compare. All of these tractors but the 101 sported the 4 cyl. engine. The 101 used a flat head 6 cyl. continental similar to the oliver 70 overhead valve continental.

I know my 1940 John Deere B is comperable to my 60 but I have seen early 1950&#039;s model b&#039;s put out the same on the dyno as my 46 oliver 70. Which mine was 30 hp on the power take off. It is stock as far as I know but I believe they were rated a little less. I would say at the time a farmer would have needed an A to keep up or possibly pass a 70.  I would recommend the book of Nebraska Tests by C.H. Wendel to compare results best. Hope that gives you more than enough info to continue your project!