I feel rather dumb needing to ask, but would feel even dumber not asking so...

I need to replace my flat, nearly inverted, leaf springs so that I can tow a 2500 lb boat. My parts list looks like that below. You see the $7 u-bolt and the $30 u-bolt. $30 u-bolt seems obnoxious to me...what does it have that the $7 one doesn't or am I totally crossing parts here? (yes, I'll be getting a pair of each)

Am I missing anything I need? Buying anything I don' need?

Crown Automotive 52000504 - Leaf Spring Bushing; Rear; $6.01
Crown Automotive 52000503 - Leaf Spring Bushing; Front; $7.76
Crown Automotive 52004010 - Axle U Bolt; 3.55 in. Wide; $6.33
Pro Comp 50050 - U-Bolt Kit; 3.5 in. Rear Lift; Incl. Hi-Nuts; Extra Thick Washers; w/Dana 35 Axle; $32.99
Crown Automotive 52000707 - Leaf Spring Assembly; For Use w/LM/ZGU/ZVU; 4 Leaf; $92.28

 

The $30 deal appears to be the set of ubolts, not just one.

 

The cheap one appears to be a single u bolt for an 8.25 axle. The more expensive one appears to be a whole set of u bolts for a Dana 35 axle.

 

See how much the same part is at rockauto.com it might be cheaper.

 

8.25" axle:
http://www.seriousoffroadproducts.co...T-KIT-3.00-X-9

D35:
http://www.seriousoffroadproducts.co...KIT-2.75-X-9-X

 

Well, that was easy.

 

Thanks everyone!