I can't comment on Isky Mega Cams but Ultradyne cams are excellent. They make a line of tight lash solid lifter cams that are specially designed for the Ford .875 diameter lifters. They work very well, produce very good torque and power and at the same time idle better than would normally be expected.
I think these days, it's hard to pick out a good cam company from a bad one. The technology has come so far in the past decade or so, that anymore all you have to do is just call a company and see what they recommend.