I was wondering if i could download 2 different versions of LFS, 0.6J and the current one on the same computer if i do a full install for the other one and just have it install somewhere else.

Yep, that would work. Two completely separated folders and shortcuts and you'll be fine.
This is also useful when you want to use a test patch while keeping the latest stable version just in case.

Thanks! ill try it out

I have several LFS installations on the same PC so you don't even need another PC.

I have all versions installed on my pc from z25 to 0.6Q and i don't have any problems also some of early versions was installed on XP but they still works fine when i change system to win 7