Downgrading from vm510pv8 to vm510pv7

[ProPro]

Hi, im new to the forums, but i know my way around technology pretty well. I have a new rumor touch for virgine mobile with the version of firmware that doesnt show the "SD CARD" folder in the "My Stuff" folder so that i can use 3rd party apps. I figure the best way to fix this is to downgrade the firmware to the previous version (which i know works). I already have my spc code and have unlocked the phone into dm mode and have lgdownloader and all that jazz, but im not sure how to the actual downgrade, or even where to get the required files. Can anyone help me with this problem?