Trans and shaft swap. Am i on crack?

My 65 Dart was small block, 727, with an 8 3/4. Trying to shave a little time off it I swapped in a 904 that i prepped for bracket racing. I had a new drive shaft made.
Now I have 727 and a drive shaft sitting around. My 70ish dart is a 340 4 speed that I want to put the 727 in so I can let my daughter bracket race it.
My question here is both darts have the same wheel base, use the same frame rails, and 8 3/4. If I put the 727 in it, in theory the drive shaft should work on my 70ish. Whats your thoughts?

Should fit.
Maybe just for the fun of it measure from the bell surface on the engine block to the 8.75 yoke and do the same with the trans and driveline while it's still out of the car.