All Bolens Tube frame attachments (assuming you have the correct brackets) will fit any of the tractors from the 16 year production. The exception to this is the 600, which has a shorter wheelbase. I believe a 600 has a wheelbase of 40 inches with the other's being 43 inches. The plans for the sleeve hitch are fine for the bracket on a 600 but you will need to make a shorter lift lever, not sure how much shorter.
We love a good Bolens mystery The 600 was made 1962-1965. From the ID tag, are you able to confirm if the model number is 181-04? The first bit of the number has to be 181-0 it's the last number which is critical. It is possible the tractor you have was made up from parts from at least one other at some point but it is too early to jump to that conclusion
Only the 1962 and 1963 models were originally painted gold and the 1962 had the throttle in the centre of the steering column, so yours is not a 1962. The 1962 model had a few other difference too. The 1964 and 1965 models were painted white and brown with some red bits. As such it is possible yours is a 1963 but if it is the model number would be 181-03.
Originally the seat would have come with a cover that goes over the metal frame. To me, the metal seat on yours looks right. Not sure about wheel size although it should be fitted with 6.00-12 and 4.00-8 tyres.
I am sure the other Bolens boys will jump in to point out any mistakes I have made with this.
Iain