Broad question from a rookie

Yes! The oversrive option is a good one but a little bit of a pain in the ***. As far as a Mopar trans goes your best bet IMO would be the A-500. It is based off of the 904 and it does require some tunnel mods.

But the OD ratio is .69. This should be multiples by the gear ratio for the new OD ratio. Or final drive. Let me illustrate;
355 gears X’s .69 OD ratio equals 2.45 final drive. Great for 200 PMH assaults.
But;
4.56’s = 3.14
4.10’s = 2.82.

Get some fat tires!

FWIW, the author of that transmission book is a member here.