Use the H/L Coupon . Buy the second parts kit. If you are a MOPAR builder, it is not like you'll not just swap the Diffs and build them both. And, at todays prices, $19.47 (the price with the H/L coupon in California) IS about equivalent to $5.99 back in the day. I'm as broke as the next guy, and watch my nickels & dimes, but I can still budget for a pair of new kits every month, when I want to.
So, let's have no more of this" 29.99 is too much" foolishness. Heck, 15 gallons of gas just cost me $52.00 this morning, and we Californians get another 6 cents per gallon added on, next Monday, July First. Prices are up everywhere.