I forwarded Ellen's post about Michael Landon, Jr.  to the Editor of Agape Press who graciously replied with the following.  I believe it puts the issue to rest.

From the editor:

Please read this response from Rebecca Grace, who wrote that article.  I believe her comments might shed some light.  – Editor, AgapePress
 
Your email inquiry concerning Michael Landon was forwarded to me by Jody Brown, editor of AgapePress. As the writer of the Michael Landon Jr. story, Jody asked me to respond to your question. I cannot answer your question regarding Michael Landon Sr. and any ties he may have had to Mormonism.

However, I can tell you from my personal conversation with Michael Landon Jr. that he is a Bible-believing Christian whose life was changed by the power of Christ. In no way did he say anything that would indicate being persuaded by the Mormon religion. Michael Jr. became a Christian just before he turned 19. The importance of Christ in his life was very evident in his responses to my questions. His publicist can attest to him being a Christian because he works directly with Michael Jr. and has seen the evidence of Christ in Michael Jr.'s life.

In addition, Michael Jr. has appeared in Christian media outlets ranging from Daystar to the 700 Club to the Hour of Power to Christianity Today. His publicist said he would be happy for you to contact him if you have any further questions. Please let me know, and I will be happy to assist you with his contact information.

On a personal note, Michael Jr. was one of the best interviews I've had simply because I was so encouraged by his love for the Lord! Of course I can't see Michael's heart and only the Lord knows the certainly of spiritual condition, but he gave me no reason to doubt the testimony he so candidly shared with me. I hope this helps.
Thank you,
Rebecca Grace