Any 3.7 block from '05 and later will work with your GC - the cam sprocket timing ring and the crankshaft reluctor ring (also a timing ring) will be the correct ones for use with your computer.
As mentioned by Nejeep the external components are what you'll need to swap over if the engine didn't come from a GC from the same year. So if you grab an engine from a Dakota for instance, look closely at the exhaust and intake manifolds, oil pan, and oil filter drain trough to see if they're different from your GC. The A/C, alternator, power steering pump and serpentine belt tensioner will just swap over from your GC engine to the replacement.
Kudos for taking on this project with your son. The project is not complicated but requires attention to detail so make sure everything is reassembled property. Attention to detail and focus are good things to teach 16 year olds - LOL!
I swapped a 2009 3.7 from a Dodge Dakota into my '03 Liberty and had to change out the things I listed above - plus break down the '09 engine and put in the correct cam sprocket and reluctor ring so they matched my computer. Even with that I did the project in my two car garage over 4 days while doing my sales calls and working evenings. Couple of buddies and my dad helped out - still have fond memories of the project and the Liberty is still going strong after 106,000 miles on the replacement engine.
2003 Renegade, Black
- 3.7L, 42RLE, 4.10's, ARB Bull Bar, Smittybilt XRC 9500lb Winch, 4X Guard Trans skid, Skid Row Engine skid, Factory T-case & Tank skids, Custom BoulderBars, JBA Front Coilovers, OME 948 rear springs, Bilstein rear shocks, JBA A-Arms, Moabs with Goodyear Duratracs 265/70-16