Another 727 build

So its time to start on the transmission and will have questions throughout the buildup since I haven't found much reference material out there.
I have a 727 from a 76 truck that Will be behind a 380-400 hp 400 lbs 360.
The tranny looks like new inside so far but has 3 pinion planets. What kind of abuse will they handle? I don't plan on beating this car.
I know the front drum is one of the weak links. Is the only upgrade option a $600 billet drum?
Are all factory drums equal? I see hemi drums advertised for sale.
What about planetary gear sets? Does anything newer fit? Like for the A518 or 46re?
Just thought I would throw those questions out there to start
Thanks for viewing