yes on a truck, 35 ton US = 70,000 pounds capacity. The problem is the outside frame, the load would have to be spread evenly both across & length wise on the deck. It is rather easy to cut it up & make a fixed neck drop deck, with moving the beams to the center. so that the run with the same width as the rails over the tri axle suspension.
Then make new deck side extensions & it would be able to haul the D8
Like Force said, square, when i ran a Mack dealership's service shop, every snow plow or RDG mixer that came in the shop with the FEPTO, the hole is always square. Factory or custom fab shop, it is just not possible to get a good seal with a round hole.
Also, all of the units i have seen & or wrenched on, the inside of the square hole has stiffener / armor plates added. this is to protect the rad in case the FEPTO shaft fails. Works along the same idea as a drive shaft loop on a race car.
Well if you want to make the model accurate, then you will need to fab a pass thru in the radiator for a shaft to connect the front bottom pulley to the Hydraulic pump. Keep in mind the age of the kit, the mixer was a after thought from the original version with the high side dump box.
The complete drive connection "FEPTO" was never included in this or the Mack DM-800 mixer kit. FEPTO = Front Engine Power Take Off.