Rebuild 904 or swap for 727?

I put 6 thin Grooved red altos in my direct drum.
I was going to use smooth frictions but
A & A transmission recommend the grooved ones.
Maybe because it's a Driver only?
BTW. I changed my transmission from a 727 to a 904 and it's one of the best improvements I've done so far!
I think mainly because it has the low gear set and adds bottom end acceleration for a city driver.
Op good luck with your car!
Good choice staying 904. Imo