this is true, MLS gaskets require a surface of 50 RA or better to seal right. I used them on my motor without resurfacing it, but that was only because i had other issues with the way my block was o-ringed and the MLS gaskets were my last shot before i went and pulled the motor and had it decked. Luckily the gaskets did the trick.
I think for you MLS gaskets would be a terrible idea, since you had a ton of passes on the car there is obviously some reason you blew the gasket, if you put the MLS gaskets on there and this happens again say 10 passes down the road its not going to be an easy fix, your gonna burn up a piston. You gotta thing of the head gasket like a fuse, I'd rather blow a gasket then burn up a piston.
What was the temperature difference when you dynoed the car and when you blew it up? The air can really mess with the air/fuel ratios and i remember reading about a few guys with lightnings who had thier trucks tuned in the summer, hammer on it for months with no problems, then in the fall when its 50 degrees at night time they hammer on it, it detonates and kicks a rod out of the motor
Also i dont think the cracked intake had anything to do with this problem, if anything it would have caused a vacuum leak
Interesting points about air temperature, yes the car was tuned in the dead heat of summer, and it was super cool when it blew. But I was watching my wideband, not on that run but a few of the others and it got rich a few times 9.5% but never went lean. No signs of detonation, heads and pistons are super clean, no damage or scarring. Spark plug readings looked great. The other thing too is that I've had this tune for two summers and probably 100+ passes.
I think I'll avoid the MLS but there are so many choices out there, composite, graphite, copper, multi-layer steel, steel core laminate, perma torque severe duty, rubber coated copper, graphite coated steel core laminate, and more.
It's weird how it blew out the bottom and not through a water passage. THe oil was clean.