Since the 42a was recent,
IF you can honestly say that all 42a are of reasonably equal value, and that all 42a are comparably wooded, then I would suggest that timber from 6a be valued as sold and show no gain/loss. the rest of the values can be easily computed therefrom.
IF, however, the land &/or timber is not closely equal for each acre, you really need an appraisal.