Currently I have a 2-row #71 planter that WAS a 4-row for years. I used it when I was planting corn to feed the cows, but stopped that nonsense about 3 years back. I cut it down to plant sweet corn and green beans.
They are about as good aplate-type planter as you'll ever find. Simple, easy to adapt to all conditions, and few moving parts to go wrong.
A few years back, most of the seed corn growers used 'em because they handled the seed so gently.
Get the manual if you don't already have one. They're abundant on Ebay.
Don't ever back up with it on the ground. The drive chains jump off the sprockets if you do.
Deere still carries some parts. If you need something they DON'T carry, contact "Yetter Manufacturing". They built these planters on contract for Deere. When Deere dropped the #71 from their product line, Yetter bought marketing rights and now sells new #71 units. They ain't cheap though.
Should you want more plates, contact "Lincoln Ag" They sell "Lustran" plates for Deere planters. (Plastic) The #71 uses what's known as "Type B" plates. Several other brands use these too.
Lincoln Ag has on their website, a cross reference chart to match their plates to Deere cast iron versions.
I have boxes of plates. I'd be willing to turn loose of a few. Contact me via PM if you're interested.