I put a crate motor in my 87 YJ. 258CID. 4.2L.
I got it from NAPA, although i'm sure you could find one for cheaper, for $2,000.
It currently has 12,000 miles on it and it runs great, money well spent.
The major reason that i went with NAPA, is that i get a Jobber Discount at my local store...