The rear shackles are the exact same width and pin diameter as a CJ7 shackle. The Eagle shackle, however, is an inch longer than a stock CJ7 shackle. You can order any CJ7 shackle advertised to lift a Jeep at least an inch.
With Monroe coil over loadlevelers and new 1970 Javelin Coil Springs up front, your Eagle will be several inches higher than it is now. I doubt you need the spacers. The Javelin springs use a thicker coil stock than the smaller AMC Passenger cars. They're available from Rockauto.
It is true that the left and right Eagle coil spring is two different sizes to compensate for the engine offset. The spring rate is actually the same, its just a difference in overall spring length. The differences in length are almost imperceptible, so most people have no issues with getting a pair of Javelin springs and putting the same spring on both sides. I use two different springs, but I buy two pairs at a time. Its not really worth buying two pairs unless you have two Eagles.