The Wallace Racing site shows engine code B1 as the base model, single two barrel carb, 283hp engine for 1961:
Year Engine HP Engine code Trans CR Cam Head Code BBL Carb No. Misc
1961 389 283 HP B1 A 10.25 472 538177 1-2 7019070 Block casting # 538181
However, that looks like a four barrel carb air cleaner in your photo. I'll look at Pete McCarthy's book later and see what it says. Someone may have swapped in the four barrel carb and manifold at some point.
The car looks pretty good - there's plenty of rust to fix but it's better than average for a '61. Is that Bristol Blue? It's the second best color for a '61, after red.
The seller appears to have a couple other 61s there in the weeds, I hope they get saved before they're too far gone.