I don't think so, as far as I understand it, the weight limit is due to the transmission, so if you put a 212 transmission in a UH-1H it can lift more, as you have more torque to play with - about 54psi as opposed to 50psi. I figure it won't make much difference at altitude as you will be limited by N1 or EGT rather than Torque anyway.
Perhaps someone else will give you a definite answer.