52 inch vs 56 inch spring hanger locations

[1969k20]

I'm in the process of turning a 71 K20 into a shortbox. I made an accident ordering the skyjacker lift in that I got the 52" rear springs instead of the 56" ones that came with it originally. I figure my only options are to send them back (paying shipping both ways) or moving the rear spring hangers forward. The problem with option 2 is that my 3/4 ton frame doesn't have the 52" hanger holes predrilled. Would anyone out there with a 1/2 ton 4x4 frame be willing to measure how many inches forward i need to drill the new holes? I would really appreciate it. Also, will grade 8 bolts be sufficient to remount the hangers to the frame? Lastly, any negatives to using the 52" springs vs the 56" ones? Ride Quality or towing capabilities? Its going to be used as a part time work truck and tow a car trailer occasionally. Just wanted to get your guys opinion if i should get the 56's or use the 52's. I attached a pic i found on this site of the measurements I'm looking for. Thank you guys!

[Mike C]

I didn't think the 56" springs came about until after the '73 model year? Interesting. I have a couple of trucks at the farm that I will put a tape to next time I am their.

Maybe Special K or someone with 3/4 ton 4x4 experience can chime in. My only experience has been with 1/2 ton 4x4 or 3/4 2x4.

[CUSTOM/10]

Are you sure that frame is a 71 K20 ? In the picture it looks like the shock mounts are on the outside of the frame rail, 71 would have been on the inside of the frame rail ?

I also agree with Mike that I believe the 56" springs didn't show up until 73, but I'm not 100% sure.

Gary

[1969k20]

You guys are 100% right. I got out and remeasured this morning and I do have 52" springs on my truck originally. I measured them several months ago and had it set in my head that they were 56". I apologize for that. I wonder why skyjacker even lists 56" ones in their catalog for 67-72 pickups. Must be a mod people do. At any rate this site is awesome and a wealth of knowledge.