If both are as good as you're saying go for it. You could pull the old engine/tranny and transfer the tranny to the donor motor and slip it back in a weekend easy.
"If you compromise the process you're an a$$hole when you start out and you're an a$$hole when you get back."
"If you don't go when you want to go, when you do go, you'll find you've gone."
"We shall meet in the place where there is no darkness."