727 or 904?

Trans builders/companies want to suggest there is a ton of black magic in these transmissions. There isn't!

Either trans has it's benefits and drawbacks.
904, smaller parts, less load holding and you can even roll the sprag and not be in danger of a front drum explosion, can safely use most every hard part inside one for a race trans sans VB.
727, bigger, stronger piece, roll the sprag and you may have a front drum in your lap or breaking a foot (google search it), expensive replacement front drum for safety ($500+), best know what you are doing if driving hard or racing, slower than a 904 due to mass.

A 904 can easily be built for under $500 with frugal shopping. The trans guys out there sell the EXACT same parts as in the transtar kits, bulkpart and WIT just at a big markup! Learn to fish or give a fish....

So simple to rebuild either unit. You could have one in the car and another on the shelf just in case.

Yep. Pick your parts, pay your money!