We are going to build a rear shock mount crossmember for our '40 chevy pickup. We have a couple inches vertical leeway on where we put the mount. How do I measure for what shocks I need? Do we build the mounts and then try to find a shock that fits or do I need to have the shocks on hand and then build the mounts? Where at between full compression and extenstion do I want the shocks to be when at rest? Is there a Napa, O'Reilly, etc. equivalent of the Pete and Jakes 1084? I do still have the lever action shocks, how do those handle? The pickup has a 9" with 60 series tires and will have a mild sbc/auto. Are they even worth trying to use? thanks-
Anytime I need 'custom' shocks I go to the local parts store and ask for the Monroe catalog. In the back is an illustrated guide with a breakdown of every part number with open and closed length and mount type (stud, saddle, bolt-on). You'll just need measurements with your rear in full travel and an idea of how you want to mount them. If I remember correctly you'll want about 60% of the travel on the top side - for rebound - I could have that backwards though. I used this method to find shocks for a bagged '46 For pickup that sat on the ground, an extremely low '51 Caddy with 4" blocks and most recently my '40 Ford pickup on customized S10 ch***is. The Caddy used a shock intended for a full size Chevy truck. I know it won't necessarily be the "correct" shock for your app but you'll save big buck over a 'lowered' shock and if you save the application/part numbers have something you can pick up at any parts store, like when I ripped out a shock on the way to the Hunnert a couple years ago - thank God 'S****s' was following me to give me a heads up and chauffer me to the local Autozone.
You don't have to have the shocks in a verticle position. You can have them sitting at an angle. Some support is lost, but unless you go too extreme of an angle, it won't matter too much. Being at an angle lets you use longer shocks. The longer shocks seem to be easier to find. I would figure out where is your best location and measure. Then hunt down a catalog as Gator says, or head to a Farm & Fleet type place where you can look at them on the shelf at your leisure. If you can't find one exact, that's where moving the angle might help with the fit. If they are gas shocks, mounting them about centered in the stroke will probably work since they have pressure in both directions. The rebound is more controlled with these. The old style only collapsed under pressure and the suspension rebound brought the shock back out. Some like the old ones because they are not as harsh on a light old car. NAPA 3033 is a short non gas shock 9 3/4-15". I have Monroe 20748 on the rear of my 39 Pontiace coupe 12 7/8-21 3/4 Gas at an angle. I have a set on the front of my 40 PU that are 10-15" gas #3749807, but I don't know the brand. On my 40 I ran a square tube across the kick up in the rear frame and drilled holes where the shocks I already had fit between the tube and the angle iron I mounted below the spring mount. I'm just rambling here, so I hope some of this stuff helps a little. I'm no expert.
Your ch***is will tell you what shock you need. If straight up, how far can the suspension compress before hitting the bump stop? How far can it droop? Add the two for total stroke. If you lean them over, measure the diagonal line on a rectangle this high, as wide as the offset of the mounts, to see how long the stroke will be. Find a shock of this stroke and then install it at the same ride height your ch***is has. It should be 1/3 to 1/2 compressed when sitting, loaded, fueled, ready to go.
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