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 a place where there is no darkness."