I wouldn't want a 4L80e with the power the L67 will put out, it doesn't make enough to really need it.

Also the gearing in the 4L80e would make it worse, first gear is way too long for what he'd want. The subaru is a very light car, even lighter than the camaro it came out of, that alone goes a long way in how well a mildly rebuilt 4L60e will hold up.