73 Dart 360 Transmission Options?

You can get adapters for a 200r4, but I'm not sure how budget-oriented that option is. Custom driveshaft, shifter, mount, bellhousing/flexplate, etc.

You can get an A500/A518 from local pick n' pulls or wrecked vehicles for fairly cheap. Has a mopar bolt pattern, takes a mopar flexplate, you just need a custom tranny crossmember and some tunnel mods. If you look for used units, the A500 is also called a 42RH and the A518 is called a 46RH. Make sure whatever unit you find ends with an RH, not RE. H stands for hydraulic control and E stands for electronic control. Pretty much any 90's dodge truck or van with a V8 should have one.