Hi brettsnz,
Firstly a warm welcome to the ODK Forum.
There are numerous things to look for, I'll put them in point order,
1 Reel condition and amount of material left for future sharpening
2 Condition of Bed Knife
3 PTO Clutch condition (see if it rotates absolutely true)
4 Condition of the chassis rails and check closely around the inner engine mounting points for fractures and visible cracks.
Wipe away any grease or oil to check thoroughly.
5 Check for flaking and blistering of the Red Powder Coating as it will have rust underneath the red layer which isn't good. The earlier Scott Bonnar versions were painted and not Powder Coated which is far better.
Production of the last Red Rover 45 finished in the 90's and all had black Briggs and Stratton engines.
Hope this gives you a good insight and feel free to write again to clarify any points of interest.
Cheers,
BB