Hello student yes you can get admission in diploma course even if you've pursue your education from Gujrat board of education as eligibility criteria says - Candidates seeking admission in diploma 3 year must passed class 10 from a recognized board.

For more updates refer to the link mentioned below
-https://www.careers360.com/colleges/government-ramchandra-khaitan-polytechnic-college-jaipur/diploma-in-mechanical-engineering-course

Feel free to comment if you have any doubt
Good luck