Many official production house channels (like Goldmines or Pyramid Glitz) have uploaded full versions of these movies for free legal viewing. Amazon Prime Video:
Many "free download" sites are hubs for malware and phishing scams. Suryavamsam Movies Download
The original film that started it all, directed by Vikraman and starring R. Sarathkumar in a dual role. It was a massive hit, winning six Tamil Nadu State Film Awards. Suryavamsam Movies Download