727 or 904?

I have a 408 (approx 480 hp) in my 68 Cuda and built a 904 for it 3 yrs. ago. I don't take it to the track much but am real hard on my car. Living out in the country gives many places to open it up. So far it's working just as good as the day I installed it. I wanted to build a trans that lasted a nice long time because my back gives me a lot of pain and R&R'ing them isn't much fun anymore. Here's what I did

1. 73 904 case hot tanked and inspected
2. Steel 4 pinion planetary gearsets front and rear (mandatory with a stroker IMO)
3. Red Eagle clutch plates and Kolene steel plates
4. My trans came with a 4 disc front clutch retainer and I had the local machinist mill the pressure plate down so I could get 5 friction discs and steel plates in it
5. Multi spring pack for the front clutch (you generally don't need this unless you spin it over 6k rpm)
6. New stock type or red lined rear band. Wide front Kevlar lined band
7. Replace all bushings and thrust washers
8. Adjust the rear geartrain end play to .008" or as close as possible. Adjust the front end play to .020" or as close as possible
9. Set rear clutch pack clearance to .030~.040". Set front clutch pack clearance to .060~.075"
10. 4.2 ratio front servo lever
11. Trans-go TF2 shift improver kit
12. Deep oil pan with filter extension. Dacron type filter
13. Good quality transmission cooler

If you machine the front clutch carrier to accept more clutches that the splines on the rear carrier engage into all the front clutch friction discs. Some rear carriers had shorter splines and won't engage all the front discs. One thing that helps extend trans life immensely is the proper installation of the shift improver kit because it boosts line pressure to the clutch packs for more holding power and eliminates shift overlap or flare up.

You might want to check out this book from Tom Hand. It has a lot of great info on building torqueflites

https://www.amazon.com/dp/1613253354/?tag=fabo03-20

I usually buy my major rebuild parts at either www.bulkpart.com or www.wittrans.com
Specialized parts can be bought from A&A trans