No particular problems, except that the tune would be wrong the for 5.0L, so timing and fueling would be poor in some areas. The GM PCMs and TBI were and still are fine for what they do, but without tuning software, emulator and chip burner, you're stuck. Even with them (and their cost), the system is very limited on what it can do. Generally, an aftermarket system with easy tuning interface is preferred, and carries features that are very useful, such as wide-band O2 support.
Some seemingly minor features can make a huge difference in frustration and effectiveness, such as that $85 WBO2 setup and a system that can use it, log viewable run results, and auto-tune with it. This makes for a much easier and more effective system, and turns the old process of total-tuning carbs or basic EFI from a big and intense (and often costly) job, into a fun weekend. Just the ignition control, or the whole setup, they are similar to the MicroSquirt in many ways, but less expensive. They can also connect into the GM harness if you like, a 5.0L harness, or a "minimal" harness you make yourself (my preference). You might want to start with simple ignition control for now and decide if you want to add fuel later. I think you are the type that won't regret that direction.
PS: I don't make any money on this stuff, and I'm happy to help, including some tuning advice and assistance. On-site tuning services are a different animal.
I always have various extra ECMs and can make you a nice deal at-cost to make some space around here.