I used one to install my 428. Somehow I did manage to strip one of the 4 carb mounting holes which subsequently required a helicoil. I'm not sure that was the fault of the engine lift plate though. I had my manifold ceramic coated and I think some of the ceramic coating got inside the bolt hole. I suspect I cross threaded the bolt as I mounted the engine plate.
I don't recall. Are those bolts 1/4 inch or 5/16? Check out this web site.
http://dodgeram.org/tech/specs/bolts..._strength.html
If they're 1/4 inch, grade 5 doesn't this chart say they wouldn't break until you hang 15,200 lbs on them (3800X4). Of course that doesn't mean the aluminum intake manifold wouldn't strip much sooner. In any case, I think you have a pretty wide margin of error and they should be plenty safe.
Chris