Check out www.atk-engines.com they have long blocks for jeeps for $1595 shipped right to your driveway. Core around $350. I have one with 15k on it and haven't had any problems. Website could be www.atkengines.com if above link doesn't work. Good luck.
I've got 155,000 miles on my Jasper engine. 10,000 more miles and it will have outlived the original engine. They are a bit more pricey these days but they seem to work and have a good warranty. :cheers: