I am a great believer in "if something works reliably, follow the same design"

Obviously you need to be aware of copyright, intellectual property etc.

For small hardware chips, the manufacturers publish reference designs. So you really do not need to worry about IP.

However finding a maverick design on the internet is not unknown.
Make sure you use a design that appears very often, and is well known and respected. The 8051 is over 30 years old !!

Good luck with your 8051 project.

David.