‘73 Dart Sport Rear End Upgrade

I’m looking for advice on which route to take. I currently have the stock 7 1/4 rear end. The previous owner upgraded the engine to a 360, but kept the weak 7 1/4. What is the best option for an upgraded rear end? Best being affordable and also available with a little luck. I’ve been looking around and 8 3/4’s in SoCal are nearly impossible to come by, especially big bolt pattern A body rear ends. Is it best to find a B body rear end and have it shortened? Also, if there are any SoCal folks on here reading this, where’s some spots that might have 8 3/4 rear ends? Everywhere I’ve called is expensive AF for just the diff. Any help would be appreciated.