When my 3.5 bit the dust, I purchased a remanned long-block here.

http://www.rhinoengines.com/isuzuengines.htm

Very good service and a good warranty too (better than Isuzu's). The product was also top-notch as noted by the dealer who did my install. The only negative comment on their part was that the pre-lube was a little light.

So far, so good for me.