I believe the best option would be a 4.0L from a 92-up XJ or Wrangler. The engines prior to 1992 were not the "HO" type, using a different cylinder head and the Renault-Bendix (Renix) fuel injection. You want a donor that uses the 92-on Mopar MPI and the HO cylinder head. Check the cylinder head casting - the 0331 head (ca 2000) was prone to cracking in its first few years, so be aware of that. New replacement cylinder heads (improved casting) are fairly cheap, so a donor from this era with a cracked head could be a good choice. '92-99 should be a safe bet, and '96-on has a better (stiffer) block).
I know the WJ guys complain that the 1999-on 4.0Ls are less durable than the earlier ZJ engines, due to the head issue and breaking piston skirts? The GCs have some different block configurations that may not drop in for the 258 - but I'm no expert in this area. If you find a candidate donor, you could check it out by posting on JeepStrokers.com - JeepStrokers also has useful FAQ postings that describe the component parts. NAXJA is another possible place to ask. However, I don't know of any place on the net where there's a table listing the issues of each of the possible donors wrt a 258 swap. So if you find an unusual donor, you'll likely have to check it out by asking for specific info. Make sure the engine mount brackets are going to work, if you find, say, a 2004 Grand Cherokee.
The accessories and beltage (is that a word?) will change based on the donor, so you'll have to decide whether you want to swap over all the donor's accessories, or keep your 258 accessories. For example, the fan offset may be different in your donor - definitely an XJ donor will have a different fan offset - but you could use the stuff off the XJ if you fit an electric fan.
1) '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps. 2) '82 J20 360/T18/NP208/3.73, KOs, 7600 GVWR 3) '75 CJ-6, 304/T15, PS, BFG KM2s, soft top 4) '95 VW Golf Sport 2000cc 2D