Here I've restored a Dinky Blaw Knox heavy tractor back to it's former glory. Dinky produced this model from 1954 to 1959. The first photo shows the condition I found it in (along with some other yard sale finds that day).
The tracks are from a supplier in the UK made specificly for the Blaw Knox model. They carry a full range of parts for vintage Corgi and Dinky models. The driver is also a replacement from the same supplier.
I think you are pretty close on the year of the Tonka catalog 1970 or so I'd say. I also found an old Hot Wheels one from 1970 (last pic).
Really nice work Junkman. Never knew anyone made any Blaw Knox heavy duty equipment. My grandpa Cooley retired as a master diesel mechanic at the near by BN plant over in Mattoon, Illinois. The plant was later shut down about 5 years or so ago. Thanks for the post and pics, it brought back a lot of good memories of my grandpa.