gas to flex 98 gc sport

Hi all, this is my first post, and have a question. I have a 98 gc sport that is flex fuel. Is there any difference between the gas and the flex other than the fuel system? I want to rebuild another engine to replace mine and want to make sure I can use a gas and just use my fuel system. Dumb question maybe, but I want to be sure before I spend the money.

Bump