904: should I switch to 727?

Keep the 904.
Even better if you can find a 999 or 998 from the late 70's to early 90's (Basically a beefed up 904 the 1980's version had wide-ratio 1st & 2nd gears, 2.74/1.54/1.0 vs. the normal 2.45/1.45/.1.0 1st, 2nd and 3rd gears)
--A lot of the F, M & J platform cars in the late 70's & 80's had these as well as V6 magnum Dakotas and some vans etc. For Example mine came out of a *1988 Dodge Diplomat Police Cruiser. (Plymouth Gran Fury was the "corporate twin")
I've been daily driving a 10.2 compression 360 with it for nearly 60,000 miles. No issues. Done many 500+ and 1000+ mile trips, it has never let me down.
Mine was rebuilt using a deluxe HP rebuild kit Kevlar bands, kolene steels and red eagle clutches.
I also put in a stage 2 Cheetah valve body kit from Turbo Action.
The ole' transmission tech who helped me rebuild mine (he's been doing it for over 30 years) assures me that mine can easily handle the 450+ hp 408 stroker I'm building at the moment.
---> He did tell me to get rid of the 8 1/4 rear axle that have. (I also have an 8 3/4 that I'm assembling)
Don't get me wrong the 727 is a good transmission it's just heavy and soaks a bit more horsepower than the 904. (I read somewhere that it's like 45 hp vs. 24 hp)
There's a guy locally here in UT that I talked to years ago at a car show, he had a 490HP 3G Scat Pak Hemi bolted to a modified 904 and has no issues.
-- (yes the new 3G hemi's will bolt up to a SBM pattern transmission, they just don't utilize the 12 o'clock bolt and need a spacer due to crank offset)
This is not the exact site I used in the past but something similar: A904 HP Rebuild Kit A998 A999 Master Banner Overhaul Automatic Transmission Dodge Chrysler Jeep

*Those Diplomats & Gran Fury's were sure ugly but in a kind of a lovable way (like a warthog), but they do make great unassuming "Sleepers" (they do have a following with respect to the dippy.org goons)
Nothing like watching a some young guys face when his new Mustang GT gets left in the dust by some ugly 1980's Minecraft looking monstrosity of a car.