i had a Ford and i tried all sorts of stuff to fix a small crack. none of them worked for long (more than a week or so).
on my YJ the manifold was cracked so that, if it weren't for the "skirts", it would have been in 3 pieces. found a replacement on the net for ~100 bucks, iirc
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.