Ill try to find it when on pc. Tho I remember reading posts of some ppl who trai ed with him, who confirmed that hes one of the sytongest bodybuilders out there and claimed seeing him lift some insane weights. Keepong in mind hes shredded too..
I have seen a video of him incline pressing in the second room at Gold's with another guy. In this one, he goes over four, yes, but he's not repping at all and his effort is monstrous. As well, he isn't close to being in ripped condition. The video was from a time when a lot of his "press" was focussing on his powerlifting and indeed he was clearly mostly focussed on pure strength training.
At his strongest, from what I've seen and know, I'd imagine Mike could incline press perhaps, say, around 365 for an intense eight? Still incredibly strong, but miles from repping four like it's nothing.