SB Cam Thrust Plate P5249637 no longer made? Only tensioner now?

You're correct. A double roller will stretch less because of it's strength. As the chain wears and stretches the cam timing will change whether it has a tensioner or not and yes the tensioner guides are not as wide as a double roller chain. You can use one if you like. It will work as designed. I just don't think I will use one again for the above reasons.
My car is a drag only car and I am using a milodon gear drive.
I was just curious on why you don,t like the tensioners. Cheers