Drivetrain upgrade options?

[Estebot]

You can shim the rearend or weld it for a locked rearend. There are a bunch of different gear ratios available for the stock 6.3 rearend that you have.
Do you know what ratio you have now? There is 4.1, 3.9', 3.7, 3.58, 3.41,
Nobody is giving up their gts disk brake rear but you can make one yourself really easily.

[toyotero2dend]

The rear end out of the corolla gts is a direct bolt on to the Te72
I had that swap on my car rode great on the highway also local.