A-904, 998, 999

I have a '85 lock-up behind my 318 and from what I read here, that makes the tranny a 998, or 999. What the difference between the two, I have no idea.

I also read that some folks here changed over their lock-up to a non-lock up allowing them to run any 904 converter. Also, I understand that this year of tranny has a low gear set. So does that mean it has the 2.77 first gear set?

Anyways, just looking to change my lock up to a non- lock so I can run a better converter for my semi hot 318 with a 3.55 gear'd 3700 body.

Thanks for any input.