Making The Weak 7-1/4 Rear Axle Live... Kinda

Howdy!
I have a challenge for my self and would like some constructive input.
I'm building a 318 for my 73 Dart, it should make somewhere in the ballpark of 300HP. It will be bolted to the A904 auto transmission with a stock-ish stall converter. The car's weight is somewhere around 3450 pounds with driver.

So, I don't have a stronger rear yet, so the challenge becomes making the 7.25 rear hold up in the meantime. So far I know the spider gears in the diff are pretty weak, so let's start there. I have some ideas, like:
Welding the spiders together.(May not be good for street use)

Somewhow converting the open diff to a LSD.(Will be lots of research to be done for cheap)

Tuning the car to accelerate softer from a stop.

Not driving like an idiot.

Now before anyone replies with "Go buy a Dana 60 or Ferd 8.8" please understand that this is for fun and I'm not running a torque monster of an engine.