Rebuilding engine

I am rebuilding my engine after finding the damage and was wondering what is the best way to break the engine in after rebuild. I was told by another rzr owner that he rebuilt his and just ran regular 10w-40 oil in it and never had a problem, since I was already using polaris oil with synthetic, wouldnt it be hard on my bottom end bearings since they are use to synthetic, its hard for me to get 0w-40 sythetic and i would like to use a 10w40 sythetic.

polaris says to run 5-40 now but i still run 0-40 moble1 and walmart filter.
i always break a motor in how im going to run it. but just dont hold it at the same rpm for longer than 20-30sec.

what heat cycles should i use and how long on each?

HRR is just finished mine and started it up yesterday. He tuning the fuel manager. He has specific way to break it in. I do remember him saying not to run just one speed long. Contact him for info, if it was burning oil (rings) I would highly recommend two separate air filters that will save your engine in the long run. Hope this helps