Currently my car has no AC in the engine compartment.. What are good options for placing 1 there. Would it matter if I want toconvert to a Serpentine 4.0 stroker in the distant future?
You could switch to 4.0 Serpantine sooner than later, but it's tricky. The 4.2L crank snout needs to be cut with a grinder to shorten it about 3/4". It's less critical of a cut than you would think, although it makes sense to be hesitant before taking a grinder to your crank. It's possible to put 4.2L V-belts back on a 4.0 length crank snout, but you need the right size washers to make up for the difference in length.
Once you get the wider harmonic balancer on the front, you'll need to make a very simple change to your bolt on the timing chain cover. I think I remember it being that one threaded hole becomes a through hole or a through hole gets drilled out to let a nut sit on the backside. I forget which is which but it's obvious if you take pictures of the two.
Then you can bolt up the AC bracket and alternator brackets on the passenger side of the block. At this point you'll find at least three different types of 4.0 AC pumps and at least two different types of brackets. Later styles like my 2000 XJ has a combined block where both AC hoses connect. Early styles like my 1992 XJ have a pump that should accept AMC Eagle hoses by changing the adaptors. A joint hose middle style has an AC Pump that can have the back half of it removed and swapped with the 1992 style to use those same seperate adaptors.
As far as brackets go, you will find another big challenge. The 4.0 block has two threaded bolt bosses in that corner that the 4.2 block never had. The 1992 XJ style of alternator bracket bolts to those missing bolt bosses on one side and then the AC pump bracket on the other side. It is really weak and shaky without those bolts. A 1995 abouts XJ will have a different Alternator bracket that still uses those bolts, but also has a more rigid connection to the AC bracket. With that type you can just stiffen it a little bit with a bolt with two nuts and washers that let you push the bracket from the block instead of bolting it.
Your 4.2 intake manifold bolts will not line up quite right, but it's a minor change to make new holes in the power steering bracket. You'll have to use the 4.0 power steering pump but the AMC Eagle steering box and hoses are perfectly compatible with it.
Sounds like alot, but it's not too bad. The wider 4.0 serpantine is much stronger and much less likely to ever squeal. I hate V-belts enough to go through all this.
If I was to refurbish AMC Eagles for resale, I would make them all with 4.0 blocks, 4.2 flywheels, T5 transmissions, 4.0 serpantine belts, 4.2 intakes, 4.0 exhaust headers, GM HEI dizzys, and GM Throttle Body Injection utilizing a stock Chevy fuel pump mounted at the bottom of the AMC Eagle fuel pickup line. The 4.0 blocks give you cheap performance camshafts and heads as well as ease in using serpantine belts. The TBI gives negligible performance differences to both 4.0 MPI and 304 V8 performance without any of the hassle or complexity and less than a third the cost.
The T5 manual transmission is the perfect complement to the size of the car and yet it is the cheapest and easiest to source and rebuild than all the other options. It is only lacking when it comes to MPI because it is difficult to mount the necessary Crank Position Sensor. The TBI doesn't need this sensor, however, so it complements the T5 perfectly to make a car with nearly the exact same elevated performance with considerably less time and cost to create.
Since that is the arrangement that I consider the most sensible and high performance for low cost, you're not too far off by looking at serpantine belts. Instead of buying the belts and brackets, you're better off finding an entire 4.0 engine and then putting it in your Eagle with the 4.2L flywheel and intake manifold. That's a huge upgrade for very little cost or swap complexity.
You can get a Hesco spacer to push the balancer back on the snout, so there's no machining necessary for serpentine belts from a 4.0.
Hesco Crankshaft Damper Spacer (http://www.hesco.us/shop.asp?action=details&inventoryID=45565&catId)
You need the pulleys and idlers, as well as a reverse rotation water pump. Not sure what brackets need swapped, I've never tried it myself.
Eggs for reminding me about the water pump, BenM. That's pretty important. You need the water pump to match the pulley donor vehicle. A Wrangler and some Grand Cherokees have fans on the pump, XJ's have a pulley there and the fan offset. All of them are slightly different from the 4.2L pump and reverse rotation.