Hello N8Scafe
No; the dash fire is not related to current issues.
Why pull the engine?
The ring gear is damaged and needs to be replaced.
Removing the transmission would be my choice.
The damage to the flywheel ring gear teeth; is caused by incomplete gear engagement, (the starter gear did not go deep enough to make full contact).
Please; you are confusing the issue by using the wording "the engine completely seized up", if it is seized up, that implies that the pistons will not move in the block, is this the case?????

From your description; the starter motor jammed the flywheel ring gear teeth, which locked the engine momentarily????
If the starter motor jammed the flywheel ring gear teeth, you have a dead short across the battery, each time you attempt to start, the battery overloads, warping the plates and generates hydrogen gas = Boom, one spark from overheated warped battery plates and you have a mini sulphuric acid bomb, very dangerous.

Replacement of the flywheel does not require engine balancing.
There are good instructions to replace a flywheel, look in your Chilton’s under Flywheel or transmission removal.
Have a great day.

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