I think this is a great idea. I like "because I can" projects!
Have you considered sticking a 4L80 or even a 6 speed in it since your swapping everything any way?
Thought about it, yes. But that's about as far as the idea has gone.
I know the 80E is a stouter trans but the 60E held up fine for me...
Now a 6 speed is enticing and I would enjoy the extra gearing especially since I'm rolling 4:11's. Not sure how final drive relates to a 60E though?

.
I'll make an extra effort to send you two pictures.