Choices to make. I can easily see rebuilding that 289 Ford sucking up much of that 5G budget these days, and then the question of the real condition of the trans will be at the back of my mind. The Chevy motor & trans works now. I'm a Mopar guy, so I have no preference in this deal.
From strictly a budget standpoint, the GM motor/trans will get the project to the road much faster because you at least stand a chance staying with in the budget.
If the set budget is flexible, or a guy doesn't mind slowing down the build process to get his choice of motor, that changes everything.
Also, if a guy really wants a specific brand of drive train, moving forward on things that can be done while searching for the desired drive train may pay off big time.
When I started building my 49 Dodge, I did not have a motor or trans at all! About a month into the build, totally unexpectedly, I was offered a 44,000 mile, complete, 318 drive train for $400 (that included the 44,000 mile parts truck as well, the frame was rotted out).
Sometimes needed parts just show up at the right time. We are rat rodders, it has happened to all of us at some point.