Okay, I have some questions about the 8n flathead.

My father in law has an 8n flathead 335xxx the model number on the head is J83. It has been repaired over the years and has developed another leak since he bought the tractor. We found a guy parting out his 8n model number 438xxx and head number M51 (no repairs).

We have service/owners manuals and parts catalog(CD). Being new to tractors we wanted to ensure we head down the right path. Especially, since the manuals make reference to different parts used in different years (or maybe we aren't reading that correctly).

1. Are these two heads interchangeable? Is there a way to verify this without pulling the heads?

2. The service manual makes reference to different carbs used. It appears a previous owner used what appears to be a 9n carb on the tractor. The parted out tractor has a new rebuilt 8n carb in the box. If we switch the 9n carb out to the new 8n carb, what likely problems will we run into with running or starting the tractor if any?

Forgive our questions if they are elementary, we are both part timers with the tractor as we work and only tinker with it when we have the time.