Transmission problems!!

so i had the E out bashing yesterday and it was just not sounding right so i took her home and riped the tranny apart this morning and a pin that holds one of the metal drive gears on had come loose and etched my case and the plastic idler gear the case more than the idler gear but they need to be replaced.....now i have read some about metal idler gear and that aluminium is not very good inside a tranny.....I only run stock motors and probly always will, what would be the best set up to put in since the tranny is out and all the gears are sitting here...nothing else is dammaged (gear wise) just the shaft that the pin goes (the hole on the shaft is a little big and causes the gear to be loose a little) in and the idler gear and of course the case.

sorry about this being so long but i just want to know what would be best (strongest) for my setup...thanks in advance.

Granden:035: