well your deck is a 42!!! the engine is either a 17 or a 17.5, so a lth1742 would be a good possibility...
I would agree with you, however the control layout and mower fascia that the 1742 manual shows don't match up with this model, the 1842's do. So either I got some mid model year Frankenstein, or a redneck Frankenstein mower. who knows. It's possible the under-hood model matches up, the prior owner wore out the 48" inch deck and popped a 42" on there...