The Super MTA was the first collector tractor I owned. I was looking for a tractor with more HP than the light utility Ford I owned to use for putting up hay. I gave $4000 for it a dozen years ago and have never had to do more than replace one battery and change fluids. A $900 baler, $500 NH rake and a $35 JD #5 mower (talk about weak links!) completed the package. I laid out about $1000 over the next six months accumulating wagons. I had been told by a neighbor who had farmed in the area with his dad that I would need at least $35,000 in equipment just to get started. I don't ask him for advice anymore.
My SMTA has a rear combo as pictured in the ebay auction referenced below. It is the same unit that is listed in the parts manual so pretty confident it would get by the correct police. Correct or not, I have put them on my Loboy, Super AV and B also. I have a spare that will go on the 300U when I get a chance. Caution when you buy these as many think they are made of gold and price them accordingly. Also, what you think is a small part can actually be expensive. Many are sold for top dollar without the knob on top. Steiner gets $10-15 for those knobs. Just saying, make sure it is complete or priced accordingly.
Just sold off my #5 mowers this year to a young fella just starting in hay. I used them 5 years and if I never see another it will be too soon. All the rest of that equipment is still on the field.